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IB Maths Analysis & Approaches · Standard Level · Topic 5

Calculus

Original questions in the style of Papers 1 and 2, each with a full worked mark scheme. Tick questions to build a printable test. Topic 5 at Higher Level →

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Original questions in the style of each exam boardFull worked mark schemes with method and accuracy marksCreated by Evan Kotronis with AI assistanceUpdated 14 October 2026 · new questions added continuouslyFree access until 30 November 2026How every question is checked →

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1AASL5-q00015.1 Limits and the derivative Paper 1Easy5 marks

Let \(f(x)=x^{2}+3x\). The point \(\text{A}(1,\,4)\) lies on the graph of \(f\). The point \(\text{B}\) also lies on the graph of \(f\) and has \(x\)-coordinate \(1+h\), where \(h\neq0\).

(a)

Show that the gradient of the chord \([\text{AB}]\) is \(5+h\).

(2)
(b)

Write down the limit of the gradient of \([\text{AB}]\) as \(h\to0\).

(1)
(c)

Find \(f'(x)\) and hence verify that \(f'(1)\) is equal to your answer to part (b).

(2)
Show mark scheme
WorkingMarkNotes
(a)
\(f(1+h)=(1+h)^{2}+3(1+h)=4+5h+h^{2}\)M1Award for a correct expansion of \(f(1+h)\).
gradient \(=\dfrac{4+5h+h^{2}-4}{(1+h)-1}=\dfrac{5h+h^{2}}{h}\)A1
\(=5+h\)AG
(b)
\(5\)A1
(c)
\(f'(x)=2x+3\)A1
\(f'(1)=2(1)+3=5\), which equals the limit in (b)A1Must see the substitution.

Answers: (b) \(5\) · (c) \(f'(x)=2x+3\), \(f'(1)=5\)

2AASL5-q00025.1 Limits and the derivative Paper 1Easy6 marks

Let \(f(x)=\dfrac{x^{3}-1}{x-1}\), for \(x\neq1\). The following diagram shows part of the graph of \(f\). The open circle shows that the point \((1,\,3)\) does not lie on the graph.

xyO1−22−137y = f(x)
(a)

Write down the value of \(\displaystyle\lim_{x\to1}f(x)\).

(1)
(b)

Explain why \(f(1)\) does not exist.

(1)
(c)

By expanding \((x-1)(x^{2}+x+1)\), show that \(f(x)=x^{2}+x+1\) for \(x\neq1\).

(2)
(d)

Hence find the gradient of the graph of \(f\) at the point where \(x=2\).

(2)
Show mark scheme
WorkingMarkNotes
(a)
\(3\)A1
(b)
substituting \(x=1\) gives \(\dfrac{0}{0}\) (division by zero is undefined)R1Accept “\(x=1\) is not in the domain” or “the denominator is zero when \(x=1\)”.
(c)
\((x-1)(x^{2}+x+1)=x^{3}+x^{2}+x-x^{2}-x-1\)M1
\(=x^{3}-1\), so \(\dfrac{x^{3}-1}{x-1}=\dfrac{(x-1)(x^{2}+x+1)}{x-1}\) and the factor \(x-1\neq0\) cancelsA1
\(f(x)=x^{2}+x+1\) for \(x\neq1\)AG
(d)
\(f'(x)=2x+1\)(M1)
\(f'(2)=5\)A1

Answers: (a) \(3\) · (b) \(\frac{0}{0}\) is undefined · (d) \(5\)

3AASL5-q00035.1 Limits and the derivative Paper 1Easy5 marks

A spherical balloon is being inflated. When its radius is \(r\) cm, its volume is \(V\ \text{cm}^{3}\), where \(V=\dfrac{4}{3}\pi r^{3}\).

(a)

Find \(\dfrac{\mathrm{d}V}{\mathrm{d}r}\).

(1)
(b)

Find the value of \(\dfrac{\mathrm{d}V}{\mathrm{d}r}\) when \(r=3\). Give your answer in terms of \(\pi\).

(1)
(c)

Interpret your answer to part (b) in context, including its units.

(1)
(d)

Find the radius of the balloon when \(\dfrac{\mathrm{d}V}{\mathrm{d}r}=100\pi\).

(2)
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WorkingMarkNotes
(a)
\(4\pi r^{2}\)A1
(b)
\(36\pi\)A1
(c)
when the radius is 3 cm, the volume is increasing at a rate of \(36\pi\ \text{cm}^{3}\) per cm increase in the radiusR1Must refer to rate of change of volume with respect to radius and give units cm3 per cm (or cm2).
(d)
\(4\pi r^{2}=100\pi\Rightarrow r^{2}=25\)(M1)
\(r=5\) cmA1Award A0 if \(r=-5\) is also given and not rejected.

Answers: (a) \(4\pi r^{2}\) · (b) \(36\pi\) · (c) volume increases at \(36\pi\) cm3 per cm of radius · (d) \(r=5\) cm

4AASL5-q00095.2 Increasing and decreasing functions Paper 1Easy5 marks

Let \(f(x)=2x^{3}-9x^{2}+12x-5\), for \(x\in\mathbb{R}\).

(a)

Find \(f'(x)\).

(2)
(b)

Find the values of \(x\) for which \(f'(x)=0\).

(2)
(c)

Hence write down the interval on which \(f\) is decreasing.

(1)
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WorkingMarkNotes
(a)
\(6x^{2}-18x\)A1Award for any two correct terms.
\(f'(x)=6x^{2}-18x+12\)A1
(b)
\(6x^{2}-18x+12=0\Rightarrow 6(x-1)(x-2)=0\)M1Or correct use of the quadratic formula.
\(x=1,\ x=2\)A1
(c)
\(1\lt x\lt 2\)A1FT from (b). Accept \(1\le x\le 2\) or \(]1,\,2[\). Award A0 for \(f'(x)\lt 0\) alone.

Answers: (a) \(f'(x)=6x^{2}-18x+12\) · (b) \(x=1,\ 2\) · (c) \(1\lt x\lt 2\)

5AASL5-q00115.2 Increasing and decreasing functions Paper 1Easy7 marks

The following diagram shows the graph of a cubic function \(y=f(x)\). The graph has a local maximum point where \(x=-2\) and a local minimum point where \(x=3\).

xyO−23y = f(x)
(a)

Write down the set of values of \(x\) for which \(f'(x)\lt 0\).

(1)
(b)

Write down the value of \(f'(3)\).

(1)
(c)

It is given that \(f'(x)=x^{2}+bx+c\). Find the value of \(b\) and the value of \(c\).

(2)
(d)

Sketch the graph of \(y=f'(x)\), showing clearly the values of any intercepts with the axes.

(3)
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WorkingMarkNotes
(a)
\(-2\lt x\lt 3\)A1Award A0 for \(-2\le x\le 3\), since \(f'(-2)=f'(3)=0\).
(b)
\(0\)A1
(c)
\(f'(x)=(x+2)(x-3)\)(M1)Or \(4-2b+c=0\) and \(9+3b+c=0\).
\(b=-1,\ c=-6\)A1
(d)
concave-up parabolaA1
\(x\)-intercepts \(-2\) and \(3\)A1
\(y\)-intercept \(-6\)A1FT from (c). The vertex \(\left(\tfrac12,\,-\tfrac{25}{4}\right)\) need not be labelled.

Answers: (a) \(-2\lt x\lt 3\) · (b) \(0\) · (c) \(b=-1,\ c=-6\) · (d) parabola through \((-2,0)\), \((3,0)\), \((0,-6)\)

6AASL5-q00125.2 Increasing and decreasing functions Paper 1Easy4 marks

Let \(f(x)=ax^{2}+bx+3\), where \(a,b\in\mathbb{R}\). The function \(f\) is decreasing for \(x\lt 2\) and increasing for \(x\gt 2\). The gradient of the graph of \(f\) at the point where \(x=0\) is \(-8\).

(a)

Find \(f'(x)\).

(1)
(b)

Write down the value of \(f'(2)\).

(1)
(c)

Find the value of \(a\) and the value of \(b\).

(2)
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WorkingMarkNotes
(a)
\(f'(x)=2ax+b\)A1
(b)
\(0\)A1
(c)
\(f'(0)=b=-8\)A1
\(4a-8=0\Rightarrow a=2\)A1FT from their \(b\).

Answers: (a) \(2ax+b\) · (b) \(0\) · (c) \(a=2,\ b=-8\)

7AASL5-q00195.3 Differentiating polynomials and integer powers Paper 1Easy6 marks

Find \(\dfrac{\mathrm{d}y}{\mathrm{d}x}\) for each of the following.

(a)

\(y=4x^{5}-3x^{2}+x-9\)

(2)
(b)

\(y=\dfrac{3}{x^{4}}\), for \(x\neq0\)

(2)
(c)

\(y=(x-3)(2x+5)\)

(2)
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WorkingMarkNotes
(a)
\(20x^{4}-6x\)A1Award for any two correct terms.
\(\dfrac{\mathrm{d}y}{\mathrm{d}x}=20x^{4}-6x+1\)A1
(b)
\(y=3x^{-4}\)(M1)
\(-12x^{-5}\)A1Accept \(-\dfrac{12}{x^{5}}\).
(c)
\(y=2x^{2}-x-15\)(M1)
\(4x-1\)A1

Answers: (a) \(20x^{4}-6x+1\) · (b) \(-12x^{-5}\) · (c) \(4x-1\)

8AASL5-q00255.4 Tangents and normals Paper 1Easy6 marks

A curve has equation \(y=x^{3}-2x+1\). The point \(\text{P}(2,\,5)\) lies on the curve.

(a)

Find the gradient of the curve at P.

(2)
(b)

Find the equation of the tangent to the curve at P. Give your answer in the form \(y=mx+c\).

(2)
(c)

Find the equation of the normal to the curve at P. Give your answer in the form \(ax+by+d=0\), where \(a,b,d\in\mathbb{Z}\).

(2)
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WorkingMarkNotes
(a)
\(\dfrac{\mathrm{d}y}{\mathrm{d}x}=3x^{2}-2\)(M1)
\(3(2)^{2}-2=10\)A1
(b)
\(y-5=10(x-2)\)(M1)
\(y=10x-15\)A1
(c)
gradient \(-\dfrac{1}{10}\): \(y-5=-\dfrac{1}{10}(x-2)\)(M1)
\(x+10y-52=0\)A1Accept any integer multiple.

Answers: (a) \(10\) · (b) \(y=10x-15\) · (c) \(x+10y-52=0\)

9AASL5-q00335.5 Introduction to integration Paper 1Easy6 marks

A function \(f\) has derivative \(f'(x)=4x^{3}+\dfrac{6}{x^{2}}\), for \(x\neq0\). The graph of \(f\) passes through the point \((1,\,3)\).

(a)

Find \(f(x)\).

(4)
(b)

Find the equation of the tangent to the graph of \(f\) at the point \((1,\,3)\).

(2)
Show mark scheme
WorkingMarkNotes
(a)
attempt to integrate, e.g. one power increased by 1M1
\(x^{4}-6x^{-1}+C\)A1Accept \(x^{4}-\dfrac{6}{x}\). Condone the absence of \(+C\) here.
substituting \((1,\,3)\): \(1-6+C=3\)M1Must include \(C\).
\(f(x)=x^{4}-\dfrac{6}{x}+8\)A1
(b)
gradient \(f'(1)=4+6=10\)A1
\(y=10x-7\)A1Accept \(y-3=10(x-1)\).

Answers: (a) \(f(x)=x^{4}-\dfrac{6}{x}+8\) · (b) \(y=10x-7\)

10AASL5-q00345.5 Introduction to integration Paper 1Easy6 marks

Find each of the following integrals.

(a)

\(\displaystyle\int(6x^{2}-4x+3)\,\mathrm{d}x\)

(2)
(b)

\(\displaystyle\int\left(x^{3}-\dfrac{2}{x^{2}}\right)\mathrm{d}x\), for \(x\neq0\)

(2)
(c)

\(\displaystyle\int(2x+1)^{2}\,\mathrm{d}x\)

(2)
Show mark scheme
WorkingMarkNotes
(a)
\(2x^{3}-2x^{2}\)A1
\(+3x+c\)A1Penalize a missing \(+c\) once only in this question.
(b)
\(\dfrac{x^{4}}{4}\)A1
\(+2x^{-1}+c\)A1Accept \(\dfrac{2}{x}\).
(c)
\(\displaystyle\int(4x^{2}+4x+1)\,\mathrm{d}x\)(M1)
\(\dfrac{4x^{3}}{3}+2x^{2}+x+c\)A1Accept \(\dfrac{(2x+1)^{3}}{6}+c\).

Answers: (a) \(2x^{3}-2x^{2}+3x+c\) · (b) \(\frac{x^{4}}{4}+\frac{2}{x}+c\) · (c) \(\frac{4x^{3}}{3}+2x^{2}+x+c\)

11AASL5-q00355.5 Introduction to integration Paper 1Easy6 marks

Let \(F(x)=(x^{2}+1)^{2}\).

(a)

By first expanding \(F(x)\), find \(F'(x)\).

(2)
(b)

Hence find \(\displaystyle\int(x^{3}+x)\,\mathrm{d}x\).

(2)
(c)

The function \(G\) satisfies \(G'(x)=x^{3}+x\) and \(G(1)=3\). Find \(G(x)\).

(2)
Show mark scheme
WorkingMarkNotes
(a)
\(F(x)=x^{4}+2x^{2}+1\)(M1)
\(F'(x)=4x^{3}+4x\)A1
(b)
\(\dfrac{1}{4}(x^{2}+1)^{2}\)A1Accept \(\dfrac{x^{4}}{4}+\dfrac{x^{2}}{2}\).
\(+c\)A1
(c)
\(\dfrac{1}{4}(1+1)^{2}+c=3\)M1
\(G(x)=\dfrac{1}{4}(x^{2}+1)^{2}+2\)A1Accept \(\dfrac{x^{4}}{4}+\dfrac{x^{2}}{2}+\dfrac{9}{4}\).

Answers: (a) \(4x^{3}+4x\) · (b) \(\frac14(x^{2}+1)^{2}+c\) · (c) \(G(x)=\frac14(x^{2}+1)^{2}+2\)

12AASL5-q00415.6 Differentiation rules Paper 1Easy6 marks

Differentiate each of the following with respect to \(x\).

(a)

\(f(x)=8\sqrt{x}-\dfrac{2}{x^{3}}+3\)

(2)
(b)

\(g(x)=\sin(3x^{2}-1)\)

(2)
(c)

\(h(x)=\ln(2x+5)+\mathrm{e}^{-4x}\)

(2)
Show mark scheme
WorkingMarkNotes
(a)
\(4x^{-\frac12}\)A1Accept \(\dfrac{4}{\sqrt{x}}\).
\(+6x^{-4}\), so \(f'(x)=4x^{-\frac12}+6x^{-4}\)A1Award A0 if a term from the constant 3 is present.
(b)
attempt to use the chain rule, e.g. \(\cos(3x^{2}-1)\times\ldots\)M1
\(g'(x)=6x\cos(3x^{2}-1)\)A1
(c)
\(\dfrac{2}{2x+5}\)A1
\(-4\mathrm{e}^{-4x}\)A1

Answers: (a) \(4x^{-\frac12}+6x^{-4}\) · (b) \(6x\cos(3x^{2}-1)\) · (c) \(\dfrac{2}{2x+5}-4\mathrm{e}^{-4x}\)

13AASL5-q00425.6 Differentiation rules Paper 1Easy5 marks

Let \(f(x)=x^{3}\ln x\), for \(x\gt 0\).

(a)

Find \(f'(x)\).

(2)
(b)

Find the exact \(x\)-coordinate of the stationary point on the graph of \(f\).

(3)
Show mark scheme
WorkingMarkNotes
(a)
attempt to use the product rule, e.g. \(3x^{2}\ln x+x^{3}\times\ldots\)M1
\(f'(x)=3x^{2}\ln x+x^{2}\)A1
(b)
\(x^{2}(3\ln x+1)=0\)M1Setting their \(f'(x)=0\) and factorizing.
\(\ln x=-\tfrac{1}{3}\)A1Must reject or ignore \(x=0\), as \(x\gt 0\).
\(x=\mathrm{e}^{-\frac{1}{3}}\)A1Accept \(\dfrac{1}{\sqrt[3]{\mathrm{e}}}\).

Answers: (a) \(3x^{2}\ln x+x^{2}\) · (b) \(x=\mathrm{e}^{-1/3}\)

14AASL5-q00455.6 Differentiation rules Paper 1Easy7 marks

Let \(f(x)=\dfrac{x^{2}+3}{\sqrt{x}}\), for \(x\gt 0\).

(a)

Write \(f(x)\) in the form \(x^{p}+3x^{q}\), where \(p,\,q\in\mathbb{Q}\).

(2)
(b)

Find \(f'(x)\).

(2)
(c)

Find the equation of the tangent to the graph of \(f\) at the point where \(x=4\).

(3)
Show mark scheme
WorkingMarkNotes
(a)
\(p=\tfrac32\)A1Accept \(x^{\frac32}\).
\(q=-\tfrac12\)A1Accept \(3x^{-\frac12}\).
(b)
\(\tfrac32x^{\frac12}\)A1FT from their (a).
\(-\tfrac32x^{-\frac32}\), so \(f'(x)=\tfrac32x^{\frac12}-\tfrac32x^{-\frac32}\)A1Accept \(\dfrac{3\sqrt{x}}{2}-\dfrac{3}{2x\sqrt{x}}\).
(c)
\(f(4)=\dfrac{19}{2}\)A1
\(f'(4)=\tfrac32\times2-\tfrac32\times\tfrac18=\dfrac{45}{16}\)A1FT from their (b).
\(y-\dfrac{19}{2}=\dfrac{45}{16}(x-4)\)A1Accept \(y=\dfrac{45}{16}x-\dfrac{7}{4}\).

Answers: (a) \(p=\tfrac32,\ q=-\tfrac12\) · (b) \(\tfrac32x^{1/2}-\tfrac32x^{-3/2}\) · (c) \(y=\dfrac{45}{16}x-\dfrac74\)

15AASL5-q00465.6 Differentiation rules Paper 1Easy6 marks

Let \(f(x)=\ln(x^{2}+5)\), for \(x\in\mathbb{R}\).

(a)

Find \(f'(x)\).

(2)
(b)

Find the gradient of the graph of \(f\) at \(x=1\).

(1)
(c)

Let \(h(x)=\ln\left(\dfrac{(x^{2}+5)^{3}}{x}\right)\), for \(x\gt 0\). By first writing \(h(x)\) in terms of \(f(x)\), show that the graph of \(h\) has a stationary point at \(x=1\).

(3)
Show mark scheme
WorkingMarkNotes
(a)
attempt to use the chain rule, e.g. \(\dfrac{1}{x^{2}+5}\times\ldots\)M1
\(f'(x)=\dfrac{2x}{x^{2}+5}\)A1
(b)
\(f'(1)=\dfrac{2}{6}=\dfrac13\)A1
(c)
\(h(x)=3\ln(x^{2}+5)-\ln x=3f(x)-\ln x\)M1Correct use of the laws of logarithms.
\(h'(x)=3f'(x)-\dfrac{1}{x}\left(=\dfrac{6x}{x^{2}+5}-\dfrac1x\right)\)A1
\(h'(1)=3\times\dfrac13-1=0\)A1Must see substitution leading to 0.
stationary point at \(x=1\)AG

Answers: (a) \(\dfrac{2x}{x^{2}+5}\) · (b) \(\tfrac13\) · (c) \(h'(1)=3\times\tfrac13-1=0\)

16AASL5-q00475.6 Differentiation rules Paper 1Easy5 marks

A curve has equation \(y=\sin^{2}(3x)\), for \(x\in\mathbb{R}\).

(a)

Find \(\dfrac{\mathrm{d}y}{\mathrm{d}x}\).

(2)
(b)

Find the gradient of the curve at the point where \(x=\dfrac{\pi}{12}\).

(2)
(c)

Find the least positive value of \(x\) for which the gradient of the curve is zero.

(1)
Show mark scheme
WorkingMarkNotes
(a)
attempt to use the chain rule twice, e.g. \(2\sin(3x)\times\cos(3x)\times\ldots\)M1
\(\dfrac{\mathrm{d}y}{\mathrm{d}x}=6\sin(3x)\cos(3x)\)A1Accept \(3\sin(6x)\).
(b)
\(6\sin\left(\tfrac{\pi}{4}\right)\cos\left(\tfrac{\pi}{4}\right)=6\times\tfrac{\sqrt2}{2}\times\tfrac{\sqrt2}{2}\)(M1)Or \(3\sin\left(\tfrac{\pi}{2}\right)\).
\(3\)A1
(c)
\(x=\dfrac{\pi}{6}\)A1From \(3\sin(6x)=0\), \(6x=\pi\).

Answers: (a) \(6\sin3x\cos3x\ (=3\sin6x)\) · (b) \(3\) · (c) \(x=\dfrac{\pi}{6}\)

17AASL5-q00565.7 The second derivative and graphs Paper 1Easy4 marks

The diagram shows part of the graph of \(y=f(x)\). The points P, Q, R and S lie on the graph. Q is a local maximum point and R is a point of inflexion.

xyOPQRSy = f(x)

Copy and complete the table below, writing “positive”, “negative” or “zero” in each cell.

PQRS
\(f'(x)\)
\(f''(x)\)
(a)

Complete the row for \(f'(x)\).

(2)
(b)

Complete the row for \(f''(x)\).

(2)
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WorkingMarkNotes
(a)
at least two of: P positive, Q zero, R negative, S negativeA1
all four correct: positive, zero, negative, negativeA1
(b)
at least two of: P negative, Q negative, R zero, S positiveA1
all four correct: negative, negative, zero, positiveA1

Answers: \(f'\): positive, zero, negative, negative · \(f''\): negative, negative, zero, positive

18AASL5-q00575.7 The second derivative and graphs Paper 1Easy5 marks

Let \(g(x)=(x-1)^{4}+2x\), for \(x\in\mathbb{R}\).

(a)

Find \(g'(x)\) and \(\dfrac{\mathrm{d}^{2}y}{\mathrm{d}x^{2}}\), where \(y=g(x)\).

(2)
(b)

Show that \(g''(1)=0\) but that the graph of \(g\) has no point of inflexion at \(x=1\).

(2)
(c)

Write down the set of values of \(x\) for which the graph of \(g\) is concave-up.

(1)
Show mark scheme
WorkingMarkNotes
(a)
\(g'(x)=4(x-1)^{3}+2\)A1
\(\dfrac{\mathrm{d}^{2}y}{\mathrm{d}x^{2}}=12(x-1)^{2}\)A1
(b)
\(g''(1)=12(0)^{2}=0\)A1
\(g''(x)=12(x-1)^{2}\gt 0\) for both \(x\lt 1\) and \(x\gt 1\), so \(g''\) does not change sign (no change of concavity)R1Award R1 for a reason referring to the sign of \(g''\) on both sides of \(x=1\).
(c)
\(x\in\mathbb{R},\ x\neq1\)A1Accept \(x\lt 1\) or \(x\gt 1\).

Answers: (a) \(g'(x)=4(x-1)^{3}+2\), \(g''(x)=12(x-1)^{2}\) · (c) \(x\neq1\)

19AASL5-q00585.7 The second derivative and graphs Paper 1Easy6 marks

A curve has equation \(y=4\sqrt{x}+\dfrac{1}{x}\), for \(x\gt 0\).

(a)

Find \(\dfrac{\mathrm{d}y}{\mathrm{d}x}\).

(2)
(b)

Find \(\dfrac{\mathrm{d}^{2}y}{\mathrm{d}x^{2}}\).

(2)
(c)

State, with a reason, whether the curve is concave-up or concave-down at the point where \(x=4\).

(2)
Show mark scheme
WorkingMarkNotes
(a)
\(2x^{-\frac12}\)A1
\(-x^{-2}\), so \(\dfrac{\mathrm{d}y}{\mathrm{d}x}=2x^{-\frac12}-x^{-2}\)A1
(b)
\(-x^{-\frac32}\)A1FT from their (a).
\(+2x^{-3}\)A1
(c)
\(\dfrac{\mathrm{d}^{2}y}{\mathrm{d}x^{2}}\Big|_{x=4}=-\dfrac18+\dfrac{2}{64}=-\dfrac{3}{32}\)A1
\(\dfrac{\mathrm{d}^{2}y}{\mathrm{d}x^{2}}\lt 0\), so concave-downR1Do not award R1 without a correct value or sign of the second derivative.

Answers: (a) \(2x^{-1/2}-x^{-2}\) · (b) \(-x^{-3/2}+2x^{-3}\) · (c) concave-down (\(-\tfrac{3}{32}\lt 0\))

20AASL5-q00605.7 The second derivative and graphs Paper 1Easy6 marks

The diagram shows the graphs labelled A, B and C. One of them is the graph of \(y=f(x)\), one is the graph of \(y=f'(x)\) and one is the graph of \(y=f''(x)\).

xyO−22AxyO−22Bxy−22C
(a)

State which graph is the graph of \(f\), which is the graph of \(f'\) and which is the graph of \(f''\).

(2)
(b)

Write down the number of points of inflexion on the graph of \(f\). Give a reason for your answer.

(2)
(c)

Given that \(f(x)=\dfrac{x^{4}}{4}-2x^{2}\), find the exact \(x\)-coordinates of the points of inflexion on the graph of \(f\).

(2)
Show mark scheme
WorkingMarkNotes
(a)
C is the graph of \(f\)A1
A is the graph of \(f'\) and B is the graph of \(f''\)A1Reasoning: the zeros of A are at the turning points of C; the zeros of B are at the turning points of A.
(b)
\(2\)A1
graph B (\(f''\)) crosses the \(x\)-axis twice, changing sign each timeR1Accept: graph A (\(f'\)) has two turning points. Do not award A1R0.
(c)
\(f''(x)=3x^{2}-4=0\)M1
\(x=\pm\dfrac{2}{\sqrt3}\)A1Accept \(\pm\dfrac{2\sqrt3}{3}\).

Answers: (a) \(f\): C, \(f'\): A, \(f''\): B · (b) 2 · (c) \(x=\pm\dfrac{2}{\sqrt3}\)

21AASL5-q00615.7 The second derivative and graphs Paper 1Easy5 marks

Let \(y=\mathrm{e}^{-2x}+\sin(2x)\), for \(x\in\mathbb{R}\).

(a)

Find \(\dfrac{\mathrm{d}y}{\mathrm{d}x}\).

(2)
(b)

Find \(\dfrac{\mathrm{d}^{2}y}{\mathrm{d}x^{2}}\).

(2)
(c)

Show that \(\dfrac{\mathrm{d}^{2}y}{\mathrm{d}x^{2}}+4y=8\mathrm{e}^{-2x}\).

(1)
Show mark scheme
WorkingMarkNotes
(a)
\(-2\mathrm{e}^{-2x}\)A1
\(+2\cos(2x)\)A1
(b)
\(4\mathrm{e}^{-2x}\)A1FT from their (a).
\(-4\sin(2x)\)A1
(c)
\(4\mathrm{e}^{-2x}-4\sin(2x)+4\mathrm{e}^{-2x}+4\sin(2x)\)A1Must see the substitution of both \(y\) and their second derivative.
\(=8\mathrm{e}^{-2x}\)AG

Answers: (a) \(-2\mathrm{e}^{-2x}+2\cos2x\) · (b) \(4\mathrm{e}^{-2x}-4\sin2x\)

22AASL5-q00695.8 Stationary points, inflexion and optimization Paper 1Easy6 marks

Let \(f(x)=x^{4}-8x^{2}+3\), for \(x\in\mathbb{R}\).

(a)

Find \(f'(x)\).

(1)
(b)

Find the \(x\)-coordinates of the stationary points on the graph of \(f\).

(2)
(c)

By considering the sign of \(f'(x)\), find the coordinates of the local maximum point and of the local minimum points.

(3)
Show mark scheme
WorkingMarkNotes
(a)
\(f'(x)=4x^{3}-16x\)A1
(b)
\(4x(x^{2}-4)=0\Rightarrow4x(x-2)(x+2)=0\)M1
\(x=-2,\ 0,\ 2\)A1
(c)
\(f'\lt 0\) for \(x\lt -2\), \(f'\gt 0\) for \(-2\lt x\lt0\), \(f'\lt 0\) for \(0\lt x\lt2\), \(f'\gt 0\) for \(x\gt2\)R1e.g. \(f'(-3)=-60\), \(f'(-1)=12\), \(f'(1)=-12\), \(f'(3)=60\), or a correct sign diagram.
local maximum \((0,\,3)\)A1
local minima \((-2,\,-13)\) and \((2,\,-13)\)A1Both points required.

Answers: (b) \(x=-2,\ 0,\ 2\) · (c) max \((0,3)\), min \((-2,-13)\) and \((2,-13)\)

23AASL5-q00705.8 Stationary points, inflexion and optimization Paper 1Easy7 marks

Let \(f(x)=\mathrm{e}^{2x}-6x\), for \(x\in\mathbb{R}\).

(a)

Find \(f'(x)\).

(1)
(b)

Find the exact \(x\)-coordinate of the stationary point on the graph of \(f\).

(2)
(c)

Use the second derivative to show that this stationary point is a minimum.

(2)
(d)

Find the exact minimum value of \(f\).

(2)
Show mark scheme
WorkingMarkNotes
(a)
\(f'(x)=2\mathrm{e}^{2x}-6\)A1
(b)
\(2\mathrm{e}^{2x}=6\Rightarrow\mathrm{e}^{2x}=3\)M1
\(x=\dfrac{\ln3}{2}\)A1Accept \(\ln\sqrt3\).
(c)
\(f''(x)=4\mathrm{e}^{2x}\)A1
\(f''\left(\tfrac{\ln3}{2}\right)=12\gt 0\) (or \(4\mathrm{e}^{2x}\gt 0\) for all \(x\)), so a minimumR1
(d)
\(\mathrm{e}^{\ln3}-6\times\dfrac{\ln3}{2}\)(M1)
\(3-3\ln3\)A1Accept \(3-\ln27\).

Answers: (a) \(2\mathrm{e}^{2x}-6\) · (b) \(x=\tfrac12\ln3\) · (d) \(3-3\ln3\)

24AASL5-q00735.8 Stationary points, inflexion and optimization Paper 1Easy8 marks

An open-topped water tank is a cuboid with a square base of side \(x\) metres and height \(h\) metres. Its volume is \(32\ \text{m}^{3}\). Let \(S\) be the area, in m2, of the metal used to make the base and the four sides.

(a)

Write down an expression for \(h\) in terms of \(x\).

(1)
(b)

Show that \(S=x^{2}+\dfrac{128}{x}\).

(2)
(c)

Find \(\dfrac{\mathrm{d}S}{\mathrm{d}x}\).

(1)
(d)

Find the value of \(x\) for which \(S\) is a minimum, and the minimum value of \(S\).

(3)
(e)

Use the second derivative to justify that this value of \(x\) gives a minimum.

(1)
Show mark scheme
WorkingMarkNotes
(a)
\(h=\dfrac{32}{x^{2}}\)A1
(b)
\(S=x^{2}+4xh\)M1Base plus four sides; no top.
\(x^{2}+4x\times\dfrac{32}{x^{2}}\)A1
\(S=x^{2}+\dfrac{128}{x}\)AG
(c)
\(2x-\dfrac{128}{x^{2}}\)A1
(d)
\(2x-\dfrac{128}{x^{2}}=0\Rightarrow x^{3}=64\)M1
\(x=4\)A1
\(S=16+32=48\ \text{m}^{2}\)A1
(e)
\(\dfrac{\mathrm{d}^{2}S}{\mathrm{d}x^{2}}=2+\dfrac{256}{x^{3}}\), which is \(6\gt 0\) at \(x=4\), so a minimumR1

Answers: (a) \(h=\dfrac{32}{x^{2}}\) · (c) \(2x-\dfrac{128}{x^{2}}\) · (d) \(x=4\), \(S=48\ \text{m}^{2}\)

25AASL5-q00825.9 Kinematics Paper 1Easy8 marks

A particle moves in a straight line so that its displacement, \(s\) metres, from a fixed point O after \(t\) seconds is given by \(s(t)=2\sin(3t)\), for \(0\le t\le\pi\).

(a)

Find expressions for the velocity, \(v\), and the acceleration, \(a\), of the particle in terms of \(t\).

(3)
(b)

Show that \(a=-9s\).

(1)
(c)

Find the speed of the particle when \(t=\dfrac{\pi}{9}\).

(2)
(d)

Find the first time \(t\gt 0\) at which the particle is at rest.

(2)
Show mark scheme
WorkingMarkNotes
(a)
attempt to differentiate using the chain rule (factor of 3 seen)(M1)
\(v=6\cos(3t)\)A1
\(a=-18\sin(3t)\)A1FT from their \(v\).
(b)
\(a=-18\sin(3t)=-9\big(2\sin(3t)\big)\)M1Must see the factorisation linked to \(s\).
\(a=-9s\)AG
(c)
\(v\left(\tfrac{\pi}{9}\right)=6\cos\left(\tfrac{\pi}{3}\right)\)(M1)
\(3\ \text{m s}^{-1}\)A1
(d)
\(\cos(3t)=0\Rightarrow 3t=\tfrac{\pi}{2}\)(M1)
\(t=\dfrac{\pi}{6}\)A1Award A0 for \(t=\tfrac{\pi}{2}\) (forgetting to divide by 3).

Answers: (a) \(v=6\cos 3t,\ a=-18\sin 3t\) · (c) \(3\ \text{m s}^{-1}\) · (d) \(t=\tfrac{\pi}{6}\)

26AASL5-q00855.9 Kinematics Paper 1Easy6 marks

A cyclist moves along a straight path. The graph shows her velocity, \(v\ \text{m s}^{-1}\), after \(t\) seconds, for \(0\le t\le 8\). The graph consists of three straight line segments joining the points \((0,\,0)\), \((2,\,6)\), \((5,\,6)\) and \((8,\,-3)\).

tvO123456789−4−2246
(a)

Write down the acceleration of the cyclist for \(0\lt t\lt 2\).

(1)
(b)

Write down the value of \(t\) at which the cyclist changes direction.

(1)
(c)

Find the distance travelled by the cyclist in the first 7 seconds.

(2)
(d)

Find the total distance travelled by the cyclist in the 8 seconds.

(1)
(e)

Find the displacement of the cyclist from her starting point when \(t=8\).

(1)
Show mark scheme
WorkingMarkNotes
(a)
\(3\ \text{m s}^{-2}\)A1
(b)
\(t=7\)A1
(c)
area under the graph from \(t=0\) to \(t=7\), e.g. \(\tfrac12(7+3)\times6\), or \(6+18+6\)(M1)
\(30\) mA1
(d)
\(30+\tfrac12(1)(3)=31.5\) mA1FT from (c).
(e)
\(30-1.5=28.5\) mA1FT from (c). Award A0 for 31.5.

Answers: (a) \(3\ \text{m s}^{-2}\) · (b) \(t=7\) · (c) 30 m · (d) 31.5 m · (e) 28.5 m

27AASL5-q00935.10 Indefinite integrals and reverse chain rule Paper 1Easy6 marks

Find each of the following integrals.

(a)

\(\displaystyle\int\dfrac{6}{3x+1}\,\mathrm{d}x\)

(2)
(b)

\(\displaystyle\int\mathrm{e}^{4-2x}\,\mathrm{d}x\)

(2)
(c)

\(\displaystyle\int\sqrt{4x+1}\,\mathrm{d}x\)

(2)
Show mark scheme
WorkingMarkNotes
(a)
\(k\ln|3x+1|\)M1Award for a log of the correct linear function.
\(2\ln|3x+1|+C\)A1Condone missing modulus. Do not penalize the absence of \(+C\) more than once in the question.
(b)
\(k\,\mathrm{e}^{4-2x}\)M1
\(-\tfrac{1}{2}\mathrm{e}^{4-2x}+C\)A1
(c)
\(k(4x+1)^{\frac32}\)M1
\(\tfrac{1}{6}(4x+1)^{\frac32}+C\)A1

Answers: (a) \(2\ln|3x+1|+C\) · (b) \(-\tfrac12\mathrm{e}^{4-2x}+C\) · (c) \(\tfrac16(4x+1)^{3/2}+C\)

28AASL5-q00965.10 Indefinite integrals and reverse chain rule Paper 1Easy6 marks

In this question, \(x\gt 0\).

(a)

Find \(\displaystyle\int\left(6\sqrt{x}-\dfrac{4}{x}\right)\mathrm{d}x\).

(3)
(b)

Find \(\displaystyle\int\dfrac{x^{2}-3}{\sqrt{x}}\,\mathrm{d}x\).

(3)
Show mark scheme
WorkingMarkNotes
(a)
\(6x^{\frac12}\) integrated by increasing the power by one(M1)
\(4x^{\frac32}\)A1
\(-4\ln x+C\)A1Accept \(-4\ln|x|\). Do not penalise the omission of \(+C\) in both parts more than once.
(b)
\(x^{\frac32}-3x^{-\frac12}\)M1Splitting the fraction into powers of x.
\(\dfrac{2}{5}x^{\frac52}\)A1
\(-6x^{\frac12}+C\)A1

Answers: (a) \(4x^{\frac32}-4\ln x+C\) · (b) \(\tfrac25x^{\frac52}-6x^{\frac12}+C\)

29AASL5-q00975.10 Indefinite integrals and reverse chain rule Paper 1Easy6 marks

Find each of the following integrals.

(a)

\(\displaystyle\int\dfrac{1}{(2x-5)^{3}}\,\mathrm{d}x\), for \(x\neq\tfrac52\)

(2)
(b)

\(\displaystyle\int\dfrac{3}{1-4x}\,\mathrm{d}x\), for \(x\lt \tfrac14\)

(2)
(c)

\(\displaystyle\int\sin\left(\dfrac{\pi}{3}-2x\right)\mathrm{d}x\)

(2)
Show mark scheme
WorkingMarkNotes
(a)
\((2x-5)^{-2}\) seen, or factor \(\tfrac12\) seen(M1)
\(-\dfrac{1}{4(2x-5)^{2}}+C\)A1
(b)
\(\ln(1-4x)\) seen(M1)
\(-\dfrac{3}{4}\ln(1-4x)+C\)A1Accept \(\ln|1-4x|\). Award A0 for \(+\tfrac34\ln(1-4x)\).
(c)
\(\cos\left(\tfrac{\pi}{3}-2x\right)\) seen(M1)
\(\dfrac{1}{2}\cos\left(\dfrac{\pi}{3}-2x\right)+C\)A1Award A0 for \(-\tfrac12\cos\left(\tfrac{\pi}{3}-2x\right)\).

Answers: (a) \(-\dfrac{1}{4(2x-5)^{2}}+C\) · (b) \(-\tfrac34\ln(1-4x)+C\) · (c) \(\tfrac12\cos\left(\tfrac{\pi}{3}-2x\right)+C\)

30AASL5-q00985.10 Indefinite integrals and reverse chain rule Paper 1Easy5 marks

A function \(f\) has derivative \(f'(x)=4\sin(2x)\), for \(x\in\mathbb{R}\). The graph of \(f\) passes through the point \(\left(\dfrac{\pi}{2},\,5\right)\).

(a)

Find \(f(x)\).

(4)
(b)

Write down the maximum value of \(f\).

(1)
Show mark scheme
WorkingMarkNotes
(a)
attempt to integrate \(f'(x)\)M1
\(-2\cos(2x)+C\)A1
\(5=-2\cos\pi+C\)M1Substituting the point into an expression containing C.
\(f(x)=3-2\cos(2x)\)A1
(b)
\(5\)A1FT from their f.

Answers: (a) \(f(x)=3-2\cos(2x)\) · (b) 5

31AASL5-q01045.10 Indefinite integrals and reverse chain rule Paper 1Easy5 marks
(a)

Expand \(\left(\mathrm{e}^{x}+\mathrm{e}^{-x}\right)^{2}\).

(1)
(b)

Hence find \(\displaystyle\int\left(\mathrm{e}^{x}+\mathrm{e}^{-x}\right)^{2}\mathrm{d}x\).

(2)
(c)

A student writes \(\displaystyle\int\cos(5x)\,\mathrm{d}x=5\sin(5x)+C\). Explain the error and write down the correct answer.

(2)
Show mark scheme
WorkingMarkNotes
(a)
\(\mathrm{e}^{2x}+2+\mathrm{e}^{-2x}\)A1
(b)
\(\dfrac12\mathrm{e}^{2x}-\dfrac12\mathrm{e}^{-2x}\)A1FT from (a).
\(+2x+C\)A1
(c)
the student has multiplied by 5 (as when differentiating) instead of dividing by 5; differentiating \(5\sin(5x)\) gives \(25\cos(5x)\)R1
\(\dfrac15\sin(5x)+C\)A1

Answers: (a) \(\mathrm{e}^{2x}+2+\mathrm{e}^{-2x}\) · (b) \(\tfrac12\mathrm{e}^{2x}+2x-\tfrac12\mathrm{e}^{-2x}+C\) · (c) \(\tfrac15\sin(5x)+C\)

32AASL5-q01085.11 Definite integrals and areas Paper 1Easy6 marks

Find the exact value of each of the following.

(a)

\(\displaystyle\int_{1}^{4}\left(3\sqrt{x}-\dfrac{2}{x^{2}}\right)\mathrm{d}x\)

(2)
(b)

\(\displaystyle\int_{0}^{\frac{\pi}{6}}\cos(3x)\,\mathrm{d}x\)

(2)
(c)

\(\displaystyle\int_{0}^{\ln 2}\mathrm{e}^{2x}\,\mathrm{d}x\)

(2)
Show mark scheme
WorkingMarkNotes
(a)
\(\left[2x^{\frac32}+\dfrac{2}{x}\right]_{1}^{4}=\left(16+\tfrac12\right)-(2+2)\)(M1)
\(\dfrac{25}{2}\)A1
(b)
\(\left[\tfrac13\sin(3x)\right]_{0}^{\pi/6}=\tfrac13\sin\tfrac{\pi}{2}-0\)(M1)
\(\dfrac13\)A1
(c)
\(\left[\tfrac12\mathrm{e}^{2x}\right]_{0}^{\ln 2}=\tfrac12(4)-\tfrac12(1)\)(M1)
\(\dfrac32\)A1

Answers: (a) \(\tfrac{25}{2}\) · (b) \(\tfrac13\) · (c) \(\tfrac32\)

33AASL5-q01095.11 Definite integrals and areas Paper 1Easy6 marks

The functions \(f\) and \(g\) are continuous for all \(x\in\mathbb{R}\). It is given that \(\displaystyle\int_{1}^{5}f(x)\,\mathrm{d}x=8\), \(\displaystyle\int_{3}^{5}f(x)\,\mathrm{d}x=10\) and \(\displaystyle\int_{1}^{5}g(x)\,\mathrm{d}x=-3\).

(a)

Find \(\displaystyle\int_{1}^{5}\big(2f(x)-3g(x)\big)\,\mathrm{d}x\).

(2)
(b)

Find \(\displaystyle\int_{1}^{5}\big(f(x)+1\big)\,\mathrm{d}x\).

(2)
(c)

Write down the value of \(\displaystyle\int_{1}^{3}f(x)\,\mathrm{d}x\).

(1)
(d)

Write down the value of \(\displaystyle\int_{5}^{1}g(x)\,\mathrm{d}x\).

(1)
Show mark scheme
WorkingMarkNotes
(a)
\(2(8)-3(-3)\)(M1)
\(25\)A1
(b)
\(8+\displaystyle\int_{1}^{5}1\,\mathrm{d}x=8+(5-1)\)(M1)
\(12\)A1Award A0 for 9.
(c)
\(8-10=-2\)A1
(d)
\(3\)A1

Answers: (a) 25 · (b) 12 · (c) −2 · (d) 3

34AASL5-q00045.1 Limits and the derivative Paper 1Medium7 marks

Water drains from a tank. The volume of water in the tank, \(V\) litres, \(t\) minutes after draining starts is given by \(V(t)=1600-80t+t^{2}\), for \(0\le t\le 40\).

(a)

Find \(\dfrac{\mathrm{d}V}{\mathrm{d}t}\).

(1)
(b)

Find the value of \(\dfrac{\mathrm{d}V}{\mathrm{d}t}\) when \(t=10\), and interpret its sign in context.

(2)
(c)

Find the time at which the water is draining at a rate of 30 litres per minute.

(2)
(d)

Show that the tank is empty when \(t=40\), and write down the rate at which the volume is changing at that instant.

(2)
Show mark scheme
WorkingMarkNotes
(a)
\(-80+2t\)A1
(b)
\(-60\)A1
negative, so the volume is decreasing (by 60 litres per minute)R1
(c)
\(-80+2t=-30\)M1Award M0 for \(-80+2t=30\) (this gives \(t=55\), outside the domain).
\(t=25\) (minutes)A1
(d)
\(V(40)=1600-3200+1600=0\)A1
\(\dfrac{\mathrm{d}V}{\mathrm{d}t}=-80+80=0\) litres per minuteA1

Answers: (a) \(2t-80\) · (b) \(-60\), decreasing · (c) \(t=25\) · (d) \(0\) litres per minute

35AASL5-q00105.2 Increasing and decreasing functions Paper 1Medium6 marks

The following diagram shows the graph of \(y=f'(x)\), the derivative of a function \(f\), for \(-1.6\le x\le 3.2\). The graph of \(f'\) crosses the \(x\)-axis at \((-1,\,0)\), has a local maximum point at \((0,\,4)\) and touches the \(x\)-axis at \((2,\,0)\).

xyO(−1, 0)(0, 4)(2, 0)y = f ′(x)
(a)

Write down the \(x\)-coordinate of the local minimum point on the graph of \(f\). Justify your answer.

(2)
(b)

State, with a reason, the nature of the point on the graph of \(f\) where \(x=2\).

(2)
(c)

Find the set of values of \(x\) for which the graph of \(f\) is concave-down.

(2)
Show mark scheme
WorkingMarkNotes
(a)
\(x=-1\)A1
\(f'(x)\) changes sign from negative to positive at \(x=-1\)R1Award R0 for “\(f'(x)=0\)” alone.
(b)
\(f'(2)=0\) but \(f'(x)\) does not change sign (positive on both sides of \(x=2\))R1
a point of inflexion with zero gradient (stationary point of inflexion)A1Award A1 only if R1 is awarded. Also accept a statement that \(f'\) has a local minimum at \(x=2\) so \(f''\) changes sign.
(c)
concave-down where \(f''(x)\lt 0\), i.e. where the graph of \(f'\) is decreasingR1
\(0\lt x\lt 2\)A1Accept \(0\le x\le 2\).

Answers: (a) \(x=-1\) · (b) a point of inflexion with zero gradient · (c) \(0\lt x\lt 2\)

36AASL5-q00135.2 Increasing and decreasing functions Paper 1Medium6 marks

Let \(f(x)=x^{3}+3x^{2}+5x-7\), for \(x\in\mathbb{R}\).

(a)

Find \(f'(x)\).

(1)
(b)

Show that \(f'(x)=3(x+1)^{2}+2\).

(2)
(c)

Hence explain why \(f\) is increasing for all values of \(x\).

(1)
(d)

By considering \(f(0)\) and \(f(1)\), show that the equation \(f(x)=0\) has exactly one real solution, and that this solution lies between \(0\) and \(1\).

(2)
Show mark scheme
WorkingMarkNotes
(a)
\(3x^{2}+6x+5\)A1
(b)
\(3(x^{2}+2x)+5\) or expanding \(3(x+1)^{2}+2=3x^{2}+6x+3+2\)M1
\(3\big((x+1)^{2}-1\big)+5\) or \(3x^{2}+6x+5\)A1
\(f'(x)=3(x+1)^{2}+2\)AG
(c)
\(3(x+1)^{2}\ge0\), so \(f'(x)\ge2\gt 0\) for all \(x\)R1
(d)
\(f(0)=-7\lt 0\) and \(f(1)=2\gt 0\), so the graph crosses the \(x\)-axis between \(0\) and \(1\)A1
\(f\) is increasing for all \(x\), so the graph cannot cross the \(x\)-axis more than onceR1

Answers: (a) \(3x^{2}+6x+5\) · (c) \(f'(x)\ge2\gt 0\) · (d) one root, between 0 and 1

37AASL5-q00185.3 Differentiating polynomials and integer powers Paper 1Medium8 marks

Let \(f(x)=\dfrac{x^{3}-4}{2x^{2}}\), for \(x\neq0\).

(a)

Write \(f(x)\) in the form \(ax+bx^{-2}\), where \(a,b\in\mathbb{Q}\).

(1)
(b)

Find \(f'(x)\).

(2)
(c)

Find the coordinates of the point on the graph of \(f\) where the gradient is zero.

(3)
(d)

Find the set of values of \(x\) for which \(f\) is increasing.

(2)
Show mark scheme
WorkingMarkNotes
(a)
\(f(x)=\tfrac{1}{2}x-2x^{-2}\)A1
(b)
\(\tfrac{1}{2}\)A1FT from (a).
\(+4x^{-3}\), so \(f'(x)=\tfrac{1}{2}+4x^{-3}\)A1Accept \(\tfrac12+\dfrac{4}{x^{3}}\).
(c)
\(\tfrac{1}{2}+\dfrac{4}{x^{3}}=0\Rightarrow x^{3}=-8\)M1
\(x=-2\)A1
\(f(-2)=\dfrac{-8-4}{8}=-\tfrac{3}{2}\); point \(\left(-2,\,-\tfrac{3}{2}\right)\)A1
(d)
\(f'(x)\gt 0\): \(\dfrac{4}{x^{3}}\gt -\tfrac12\), considering \(x\gt 0\) and \(x\lt 0\) separately (or a sign diagram for \(f'\))M1For \(x\gt 0\), \(f'(x)\gt 0\) always; for \(x\lt 0\), \(x^{3}\lt -8\).
\(x\lt -2\) or \(x\gt 0\)A1Both intervals required.

Answers: (a) \(\tfrac12x-2x^{-2}\) · (b) \(f'(x)=\tfrac12+4x^{-3}\) · (c) \(\left(-2,\,-\tfrac32\right)\) · (d) \(x\lt -2\) or \(x\gt 0\)

38AASL5-q00205.3 Differentiating polynomials and integer powers Paper 1Medium6 marks

Let \(f(x)=ax^{3}+bx^{2}\), where \(a,b\in\mathbb{R}\). The gradient of the graph of \(f\) is \(-3\) at \(x=1\) and \(0\) at \(x=2\).

(a)

Find \(f'(x)\).

(1)
(b)

Find the value of \(a\) and the value of \(b\).

(4)
(c)

Find the gradient of the graph of \(f\) at \(x=-1\).

(1)
Show mark scheme
WorkingMarkNotes
(a)
\(3ax^{2}+2bx\)A1
(b)
substituting \(x=1\) or \(x=2\) into their \(f'(x)\) and equatingM1
\(3a+2b=-3\) and \(12a+4b=0\)A1
attempting to solve simultaneously, e.g. \(b=-3a\)M1
\(a=1,\ b=-3\)A1
(c)
\(f'(-1)=3+6=9\)A1FT from (b).

Answers: (a) \(3ax^{2}+2bx\) · (b) \(a=1,\ b=-3\) · (c) \(9\)

39AASL5-q00215.3 Differentiating polynomials and integer powers Paper 1Medium8 marks

A curve has equation \(y=x^{3}-6x^{2}+10x+1\).

(a)

Find \(\dfrac{\mathrm{d}y}{\mathrm{d}x}\).

(2)
(b)

Find the coordinates of the points on the curve at which the gradient is \(1\).

(4)
(c)

Write \(\dfrac{\mathrm{d}y}{\mathrm{d}x}\) in the form \(3(x-h)^{2}+k\) and hence write down the least possible value of the gradient of the curve.

(2)
Show mark scheme
WorkingMarkNotes
(a)
\(3x^{2}-12x\)A1Award for any two correct terms.
\(3x^{2}-12x+10\)A1
(b)
\(3x^{2}-12x+10=1\)M1
\(3(x-1)(x-3)=0\Rightarrow x=1,\ x=3\)A1
substituting their \(x\)-values into \(y\)(M1)
\((1,\,6)\) and \((3,\,4)\)A1
(c)
\(3(x-2)^{2}-2\)A1
\(-2\)A1FT from their \(k\).

Answers: (a) \(3x^{2}-12x+10\) · (b) \((1,6)\), \((3,4)\) · (c) \(3(x-2)^{2}-2\); least gradient \(-2\)

40AASL5-q00225.3 Differentiating polynomials and integer powers Paper 1Medium7 marks

Let \(f(x)=\left(x+\dfrac{2}{x}\right)^{2}\), for \(x\neq0\).

(a)

Show that \(f(x)=x^{2}+4+4x^{-2}\).

(2)
(b)

Find \(f'(x)\).

(2)
(c)

Find the coordinates of the points on the graph of \(f\) where the gradient is zero.

(3)
Show mark scheme
WorkingMarkNotes
(a)
\(x^{2}+2\cdot x\cdot\dfrac{2}{x}+\dfrac{4}{x^{2}}\)M1Award for a correct expansion with at least the middle term attempted.
\(x^{2}+4+\dfrac{4}{x^{2}}\)A1
\(f(x)=x^{2}+4+4x^{-2}\)AG
(b)
\(2x\)A1
\(-8x^{-3}\)A1Accept \(f'(x)=2x-\dfrac{8}{x^{3}}\).
(c)
\(2x-8x^{-3}=0\Rightarrow x^{4}=4\)M1
\(x=\pm\sqrt{2}\)A1
\((\sqrt{2},\,8)\) and \((-\sqrt{2},\,8)\)A1\(f(\sqrt2)=2+4+2=8\)

Answers: (b) \(2x-8x^{-3}\) · (c) \((\sqrt2,\,8)\), \((-\sqrt2,\,8)\)

41AASL5-q00245.4 Tangents and normals Paper 1Medium8 marks

Let \(f(x)=\ln(2x-3)\), for \(x\gt \tfrac{3}{2}\). The graph of \(f\) meets the \(x\)-axis at the point \(\text{P}(2,\,0)\).

(a)

Find \(f'(x)\).

(2)
(b)

Find the equation of the tangent to the graph of \(f\) at P.

(2)
(c)

Find the equation of the normal to the graph of \(f\) at P.

(2)
(d)

The tangent and the normal at P meet the \(y\)-axis at the points A and B. Find the area of triangle ABP.

(2)
Show mark scheme
WorkingMarkNotes
(a)
attempt to use the chain rule, e.g. \(\dfrac{1}{2x-3}\times\ldots\)M1
\(f'(x)=\dfrac{2}{2x-3}\)A1
(b)
gradient \(f'(2)=2\)A1
\(y=2x-4\)A1Accept \(y-0=2(x-2)\).
(c)
gradient of normal \(=-\dfrac{1}{2}\)M1FT from their gradient in (b).
\(y=-\tfrac{1}{2}x+1\)A1Accept \(y=-\tfrac12(x-2)\).
(d)
A\((0,\,-4)\), B\((0,\,1)\); base \(\text{AB}=5\), height \(=2\) (the \(x\)-coordinate of P)(M1)FT from their lines.
area \(=\tfrac{1}{2}\times5\times2=5\)A1

Answers: (a) \(\dfrac{2}{2x-3}\) · (b) \(y=2x-4\) · (c) \(y=-\tfrac12x+1\) · (d) \(5\)

42AASL5-q00265.4 Tangents and normals Paper 1Medium6 marks

Let \(f(x)=x^{2}-4x+5\).

(a)

Find \(f'(x)\).

(1)
(b)

Find the gradient of the normal to the graph of \(f\) at the point where \(x=1\).

(2)
(c)

The tangent to the graph of \(f\) at the point Q is parallel to the normal in part (b). Find the coordinates of Q.

(3)
Show mark scheme
WorkingMarkNotes
(a)
\(2x-4\)A1
(b)
\(f'(1)=-2\)(M1)
\(\dfrac{1}{2}\)A1
(c)
\(2x-4=\dfrac{1}{2}\)M1FT from (b).
\(x=\dfrac{9}{4}\)A1
\(\text{Q}\left(\dfrac{9}{4},\,\dfrac{17}{16}\right)\)A1\(\dfrac{81}{16}-9+5=\dfrac{17}{16}\)

Answers: (a) \(2x-4\) · (b) \(\tfrac12\) · (c) \(\left(\tfrac94,\,\tfrac{17}{16}\right)\)

43AASL5-q00285.4 Tangents and normals Paper 1Medium7 marks

Let \(f(x)=x^{2}-3x\). The point \(\text{P}(1,\,-2)\) lies on the graph of \(f\).

(a)

Find \(f'(x)\).

(1)
(b)

Find the equation of the normal to the graph of \(f\) at P.

(3)
(c)

The normal meets the graph of \(f\) again at the point R. Find the coordinates of R.

(3)
Show mark scheme
WorkingMarkNotes
(a)
\(2x-3\)A1
(b)
\(f'(1)=-1\)(M1)
gradient of normal \(=1\)(A1)
\(y=x-3\)A1Accept \(y+2=x-1\).
(c)
\(x^{2}-3x=x-3\)M1FT from (b).
\((x-1)(x-3)=0\)A1
\(\text{R}(3,\,0)\)A1

Answers: (a) \(2x-3\) · (b) \(y=x-3\) · (c) \(\text{R}(3,\,0)\)

44AASL5-q00295.4 Tangents and normals Paper 1Medium6 marks

The line \(y=6x+k\), where \(k\in\mathbb{R}\), is a tangent to the curve \(y=x^{3}-6x\).

(a)

Find \(\dfrac{\mathrm{d}y}{\mathrm{d}x}\) for the curve.

(1)
(b)

Find the \(x\)-coordinates of the points on the curve where the gradient is \(6\).

(2)
(c)

Hence find the possible values of \(k\).

(3)
Show mark scheme
WorkingMarkNotes
(a)
\(3x^{2}-6\)A1
(b)
\(3x^{2}-6=6\)M1
\(x=\pm2\)A1
(c)
substituting a point of contact into \(y=6x+k\), e.g. \((2,\,-4)\): \(-4=12+k\)M1
\(k=-16\)A1
\(k=16\)A1From \((-2,\,4)\): \(4=-12+k\).

Answers: (a) \(3x^{2}-6\) · (b) \(x=\pm2\) · (c) \(k=-16\) or \(k=16\)

45AASL5-q00365.5 Introduction to integration Paper 1Medium7 marks

The gradient of a curve is given by \(\dfrac{\mathrm{d}y}{\mathrm{d}x}=3x^{2}-8x+k\), where \(k\in\mathbb{R}\). The curve has a horizontal tangent at the point where \(x=2\), and passes through the point \((0,\,5)\).

(a)

Find the value of \(k\).

(2)
(b)

Find the equation of the curve.

(3)
(c)

Find the equation of the tangent to the curve at the point where it meets the \(y\)-axis.

(2)
Show mark scheme
WorkingMarkNotes
(a)
\(3(2)^{2}-8(2)+k=0\)M1
\(k=4\)A1
(b)
attempting to anti-differentiateM1
\(y=x^{3}-4x^{2}+4x+c\)A1FT from their \(k\).
\(c=5\), so \(y=x^{3}-4x^{2}+4x+5\)A1
(c)
gradient at \(x=0\) is \(k=4\)(M1)FT from (a).
\(y=4x+5\)A1FT from (a) and (b).

Answers: (a) \(k=4\) · (b) \(y=x^{3}-4x^{2}+4x+5\) · (c) \(y=4x+5\)

46AASL5-q00445.6 Differentiation rules Paper 1Medium7 marks

The functions \(f\) and \(g\) are differentiable for all \(x\in\mathbb{R}\). The table shows some values of \(f\), \(g\) and their derivatives.

\(x\)\(f(x)\)\(f'(x)\)\(g(x)\)\(g'(x)\)
13\(-2\)24
2571\(-3\)
(a)

Let \(h(x)=f\big(g(x)\big)\). Find \(h'(1)\).

(3)
(b)

Let \(p(x)=f(x)\,g(x)\). Find \(p'(2)\).

(2)
(c)

Let \(q(x)=\dfrac{f(x)}{g(x)}\). Find \(q'(1)\).

(2)
Show mark scheme
WorkingMarkNotes
(a)
\(h'(1)=f'\big(g(1)\big)\times g'(1)\)M1
\(f'(2)\times4=7\times4\)(A1)
\(28\)A1
(b)
\(p'(2)=f'(2)g(2)+f(2)g'(2)=7(1)+5(-3)\)M1
\(-8\)A1
(c)
\(q'(1)=\dfrac{g(1)f'(1)-f(1)g'(1)}{\big(g(1)\big)^{2}}=\dfrac{2(-2)-3(4)}{2^{2}}\)M1
\(-4\)A1

Answers: (a) \(28\) · (b) \(-8\) · (c) \(-4\)

47AASL5-q00485.6 Differentiation rules Paper 1Medium6 marks

Let \(f(x)=\mathrm{e}^{2x}\cos x\), for \(-\dfrac{\pi}{2}\lt x\lt\dfrac{\pi}{2}\).

(a)

Find \(f'(x)\).

(2)
(b)

Show that the \(x\)-coordinate of the stationary point on the graph of \(f\) satisfies \(\tan x=2\).

(2)
(c)

Find the equation of the tangent to the graph of \(f\) at the point where \(x=0\).

(2)
Show mark scheme
WorkingMarkNotes
(a)
attempt to use the product rule, e.g. \(2\mathrm{e}^{2x}\cos x+\mathrm{e}^{2x}\times\ldots\)M1
\(f'(x)=2\mathrm{e}^{2x}\cos x-\mathrm{e}^{2x}\sin x\)A1Accept \(\mathrm{e}^{2x}(2\cos x-\sin x)\).
(b)
\(\mathrm{e}^{2x}(2\cos x-\sin x)=0\) and \(\mathrm{e}^{2x}\gt 0\), so \(2\cos x-\sin x=0\)M1Must see \(\mathrm{e}^{2x}\neq0\) (or \(\gt 0\)) stated or implied by dividing.
\(\sin x=2\cos x\Rightarrow\dfrac{\sin x}{\cos x}=2\)A1Valid since \(\cos x\neq0\) on the domain.
\(\tan x=2\)AG
(c)
\(f(0)=1\) and \(f'(0)=2\)A1Both values needed.
\(y=2x+1\)A1FT from their (a).

Answers: (a) \(\mathrm{e}^{2x}(2\cos x-\sin x)\) · (c) \(y=2x+1\)

48AASL5-q00495.6 Differentiation rules Paper 1Medium8 marks

Let \(f(x)=\dfrac{x}{\ln x}\), for \(x\gt 1\).

(a)

Show that \(f'(x)=\dfrac{\ln x-1}{(\ln x)^{2}}\).

(2)
(b)

Find the exact coordinates of the stationary point on the graph of \(f\).

(3)
(c)

Justify that this point is a local minimum.

(1)
(d)

Find the equation of the tangent to the graph of \(f\) at the point where \(x=\mathrm{e}^{2}\).

(2)
Show mark scheme
WorkingMarkNotes
(a)
attempt to use the quotient rule, with terms in the correct orderM1
\(f'(x)=\dfrac{\ln x\times1-x\times\frac{1}{x}}{(\ln x)^{2}}\)A1
\(f'(x)=\dfrac{\ln x-1}{(\ln x)^{2}}\)AG
(b)
\(\ln x-1=0\Rightarrow\ln x=1\)M1
\(x=\mathrm{e}\)A1
\(y=\dfrac{\mathrm{e}}{\ln\mathrm{e}}=\mathrm{e}\)A1Coordinates \((\mathrm{e},\,\mathrm{e})\).
(c)
\((\ln x)^{2}\gt 0\); for \(1\lt x\lt\mathrm{e}\), \(\ln x-1\lt 0\) so \(f'(x)\lt 0\); for \(x\gt\mathrm{e}\), \(f'(x)\gt 0\); \(f'\) changes from negative to positiveR1Accept a correct sign diagram, or a valid second-derivative argument.
(d)
\(f\left(\mathrm{e}^{2}\right)=\dfrac{\mathrm{e}^{2}}{2}\) and \(f'\left(\mathrm{e}^{2}\right)=\dfrac{2-1}{4}=\dfrac14\)A1Both values needed.
\(y-\dfrac{\mathrm{e}^{2}}{2}=\dfrac14\left(x-\mathrm{e}^{2}\right)\)A1Accept \(y=\dfrac14x+\dfrac{\mathrm{e}^{2}}{4}\). FT from their values.

Answers: (b) \((\mathrm{e},\ \mathrm{e})\) · (d) \(y=\dfrac14x+\dfrac{\mathrm{e}^{2}}{4}\)

49AASL5-q00505.6 Differentiation rules Paper 1Medium6 marks

Let \(f(x)=\sqrt{x}\), for \(x\ge0\), and \(g(x)=4x^{2}+9\), for \(x\in\mathbb{R}\).

(a)

Write down an expression for \((f\circ g)(x)\).

(1)
(b)

Find \((f\circ g)'(x)\).

(2)
(c)

Find the gradient of the graph of \(y=(f\circ g)(x)\) at \(x=2\).

(1)
(d)

Show that the derivative of \((g\circ f)(x)\) is constant for \(x\gt 0\).

(2)
Show mark scheme
WorkingMarkNotes
(a)
\(\sqrt{4x^{2}+9}\)A1
(b)
attempt to use the chain rule, e.g. \(\tfrac12(4x^{2}+9)^{-\frac12}\times\ldots\)M1
\(\dfrac{4x}{\sqrt{4x^{2}+9}}\)A1Accept \(\tfrac12(4x^{2}+9)^{-\frac12}(8x)\).
(c)
\(\dfrac{8}{\sqrt{25}}=\dfrac85\)A1FT from their (b).
(d)
\((g\circ f)(x)=4\left(\sqrt{x}\right)^{2}+9=4x+9\)A1
\((g\circ f)'(x)=4\), which is constantA1Accept a chain-rule approach: \(8\sqrt{x}\times\dfrac{1}{2\sqrt{x}}=4\).

Answers: (a) \(\sqrt{4x^{2}+9}\) · (b) \(\dfrac{4x}{\sqrt{4x^{2}+9}}\) · (c) \(\tfrac85\) · (d) \((g\circ f)'(x)=4\)

50AASL5-q00515.6 Differentiation rules Paper 1Medium8 marks

Let \(f(x)=\mathrm{e}^{x}(x^{2}+k)\), where \(k\in\mathbb{R}\) and \(x\in\mathbb{R}\).

(a)

Show that \(f'(x)=\mathrm{e}^{x}(x^{2}+2x+k)\).

(2)
(b)

The graph of \(f\) has a stationary point at \(x=1\). Find the value of \(k\).

(2)
(c)

Using your value of \(k\), find the \(x\)-coordinate of the other stationary point.

(2)
(d)

Find the set of values of \(k\) for which the graph of \(f\) has no stationary points.

(2)
Show mark scheme
WorkingMarkNotes
(a)
attempt to use the product ruleM1
\(\mathrm{e}^{x}(x^{2}+k)+\mathrm{e}^{x}(2x)\)A1
\(f'(x)=\mathrm{e}^{x}(x^{2}+2x+k)\)AG
(b)
\(f'(1)=0\Rightarrow\mathrm{e}(1+2+k)=0\)M1Must see \(\mathrm{e}\neq0\) used, or \(1+2+k=0\).
\(k=-3\)A1
(c)
\(x^{2}+2x-3=0\Rightarrow(x+3)(x-1)=0\)M1
\(x=-3\)A1
(d)
\(x^{2}+2x+k=0\) has no real roots: discriminant \(4-4k\lt 0\)M1Since \(\mathrm{e}^{x}\gt 0\).
\(k\gt 1\)A1Award A0 for \(k\ge1\): when \(k=1\), \(f'(-1)=0\).

Answers: (b) \(k=-3\) · (c) \(x=-3\) · (d) \(k\gt 1\)

51AASL5-q00595.7 The second derivative and graphs Paper 1Medium6 marks

The function \(f\) is defined for \(x\in\mathbb{R}\). The diagram shows the graph of its second derivative, \(y=f''(x)\). The graph of \(f''\) crosses the \(x\)-axis at \(x=-2\) and touches it at \(x=1\).

xyO−21y = f ″(x)
(a)

Write down the \(x\)-coordinate of the point of inflexion on the graph of \(f\).

(1)
(b)

Explain why the graph of \(f\) does not have a point of inflexion at \(x=1\).

(1)
(c)

Write down the set of values of \(x\) for which the graph of \(f\) is concave-down.

(1)
(d)

It is given that \(f'(1)=0\). Determine the nature of the stationary point on the graph of \(f\) at \(x=1\). Justify your answer.

(3)
Show mark scheme
WorkingMarkNotes
(a)
\(x=-2\)A1
(b)
\(f''(x)\ge0\) on both sides of \(x=1\): \(f''\) does not change sign, so there is no change of concavityR1
(c)
\(x\lt -2\)A1
(d)
\(f''(x)\gt 0\) for \(-2\lt x\lt1\) and \(x\gt1\), so \(f'\) is increasing on an interval containing \(x=1\)R1
as \(f'(1)=0\), \(f'(x)\lt 0\) just to the left of \(x=1\) and \(f'(x)\gt 0\) just to the rightR1
local minimumA1Award A1 only if at least one R1 is awarded. The second-derivative test fails here, since \(f''(1)=0\).

Answers: (a) \(x=-2\) · (c) \(x\lt -2\) · (d) local minimum

52AASL5-q00625.7 The second derivative and graphs Paper 1Medium7 marks

A function \(f\) has derivative \(f'(x)=x^{2}\mathrm{e}^{-x}\), for \(x\in\mathbb{R}\).

(a)

Find \(f''(x)\).

(2)
(b)

Find the set of values of \(x\) for which the graph of \(f\) is concave-up.

(2)
(c)

Explain why the graph of \(f\) has no local maximum or local minimum points.

(1)
(d)

The graph of \(f\) has two points of inflexion. State, with a reason, the \(x\)-coordinate of the point of inflexion with zero gradient.

(2)
Show mark scheme
WorkingMarkNotes
(a)
attempt to use the product ruleM1
\(f''(x)=2x\mathrm{e}^{-x}-x^{2}\mathrm{e}^{-x}\)A1Accept \(x(2-x)\mathrm{e}^{-x}\).
(b)
\(x(2-x)\mathrm{e}^{-x}\gt 0\Rightarrow x(2-x)\gt 0\)M1Or sign diagram for \(f''\) with zeros 0 and 2.
\(0\lt x\lt2\)A1
(c)
\(f'(x)=x^{2}\mathrm{e}^{-x}\ge0\) for all \(x\), so \(f'\) never changes signR1
(d)
\(x=0\)A1
\(f'(0)=0\), whereas \(f'(2)=4\mathrm{e}^{-2}\neq0\)R1Do not award A1R0.

Answers: (a) \(x(2-x)\mathrm{e}^{-x}\) · (b) \(0\lt x\lt2\) · (d) \(x=0\)

53AASL5-q00675.8 Stationary points, inflexion and optimization Paper 1Medium8 marks

Let \(f(x)=3x^{4}-4x^{3}\), for \(x\in\mathbb{R}\). The graph of \(f\) has stationary points at \(x=0\) and \(x=1\).

(a)

Show that \(f'(x)=12x^{2}(x-1)\).

(2)
(b)

Find \(f''(x)\) and hence show that \((1,\,-1)\) is a local minimum point.

(2)
(c)

Given that \(f''(0)=0\), determine the nature of the stationary point at \(x=0\). Justify your answer.

(2)
(d)

Find the \(x\)-coordinate of the point of inflexion on the graph of \(f\) that has a non-zero gradient.

(2)
Show mark scheme
WorkingMarkNotes
(a)
attempt to differentiate, e.g. one term correctM1
\(f'(x)=12x^{3}-12x^{2}\)A1Must see this expanded form before the factorized answer.
\(f'(x)=12x^{2}(x-1)\)AG
(b)
\(f''(x)=36x^{2}-24x\)A1
\(f''(1)=12\gt 0\) (and \(f(1)=3-4=-1\)), so a local minimumR1
(c)
\(f'(x)\lt 0\) on both sides of \(x=0\), e.g. \(f'(-1)=-24\), \(f'(0.5)=-1.5\) (or \(f''\) changes sign at \(x=0\))R1Since \(12x^{2}\ge0\) and \(x-1\lt 0\) near \(x=0\).
a point of inflexion with zero gradientA1Award A1 only if R1 is awarded.
(d)
\(12x(3x-2)=0\)M1Setting their \(f''(x)=0\).
\(x=\tfrac{2}{3}\)A1\(f''\) changes sign at \(x=\tfrac23\) as it is a single root.

Answers: (b) \(f''(x)=36x^{2}-24x\) · (c) point of inflexion with zero gradient · (d) \(x=\tfrac23\)

54AASL5-q00685.8 Stationary points, inflexion and optimization Paper 1Medium7 marks

Let \(f(x)=x^{3}+bx^{2}+cx+d\), where \(b,\,c,\,d\in\mathbb{R}\). The graph of \(f\) has a point of inflexion at \((1,\,3)\), and the gradient of the graph at this point is \(-2\).

(a)

Find \(f'(x)\) and \(f''(x)\).

(2)
(b)

Show that \(b=-3\).

(1)
(c)

Find the value of \(c\) and the value of \(d\).

(3)
(d)

Write down the set of values of \(x\) for which the graph of \(f\) is concave-down.

(1)
Show mark scheme
WorkingMarkNotes
(a)
\(f'(x)=3x^{2}+2bx+c\)A1
\(f''(x)=6x+2b\)A1
(b)
\(f''(1)=0\Rightarrow6+2b=0\)A1
\(b=-3\)AG
(c)
\(f'(1)=-2\Rightarrow3-6+c=-2\)M1
\(c=1\)A1
\(f(1)=1-3+1+d=3\Rightarrow d=4\)A1FT from their \(c\).
(d)
\(x\lt 1\)A1\(f''(x)=6x-6\lt 0\).

Answers: (c) \(c=1,\ d=4\) · (d) \(x\lt1\)

55AASL5-q00715.8 Stationary points, inflexion and optimization Paper 1Medium9 marks

Let \(f(x)=2x+4\cos x\), for \(0\le x\le2\pi\).

(a)

Find \(f'(x)\).

(1)
(b)

Find the \(x\)-coordinates of the stationary points on the graph of \(f\).

(3)
(c)

Use the second derivative to determine the nature of each stationary point.

(3)
(d)

Find the greatest value of \(f(x)\) for \(0\le x\le2\pi\).

(2)
Show mark scheme
WorkingMarkNotes
(a)
\(f'(x)=2-4\sin x\)A1
(b)
\(2-4\sin x=0\Rightarrow\sin x=\dfrac12\)M1
\(x=\dfrac{\pi}{6}\)A1
\(x=\dfrac{5\pi}{6}\)A1
(c)
\(f''(x)=-4\cos x\)A1
\(f''\left(\tfrac{\pi}{6}\right)=-2\sqrt3\lt 0\), so a local maximum at \(x=\tfrac{\pi}{6}\)R1
\(f''\left(\tfrac{5\pi}{6}\right)=2\sqrt3\gt 0\), so a local minimum at \(x=\tfrac{5\pi}{6}\)R1
(d)
comparing the local maximum \(f\left(\tfrac{\pi}{6}\right)=\tfrac{\pi}{3}+2\sqrt3\) with the endpoint value \(f(2\pi)=4\pi+4\)M1\(f\) is increasing for \(\tfrac{5\pi}{6}\lt x\le2\pi\).
\(4\pi+4\)A1Award M0A0 for \(\tfrac{\pi}{3}+2\sqrt3\).

Answers: (b) \(x=\dfrac{\pi}{6},\ \dfrac{5\pi}{6}\) · (c) local max at \(\tfrac{\pi}{6}\), local min at \(\tfrac{5\pi}{6}\) · (d) \(4\pi+4\)

56AASL5-q00745.8 Stationary points, inflexion and optimization Paper 1Medium9 marks

Let \(f(x)=x\mathrm{e}^{-x}\), for \(x\in\mathbb{R}\).

(a)

Find \(f'(x)\).

(2)
(b)

Show that \(f''(x)=(x-2)\mathrm{e}^{-x}\).

(1)
(c)

Show that the graph of \(f\) has a point of inflexion at \(x=2\).

(2)
(d)

Find the equation of the tangent to the graph of \(f\) at the point of inflexion.

(3)
(e)

Write down the \(x\)-coordinate of the point where this tangent meets the \(x\)-axis.

(1)
Show mark scheme
WorkingMarkNotes
(a)
attempt to use the product ruleM1
\(f'(x)=\mathrm{e}^{-x}-x\mathrm{e}^{-x}\)A1Accept \((1-x)\mathrm{e}^{-x}\).
(b)
\(f''(x)=-\mathrm{e}^{-x}-\left(\mathrm{e}^{-x}-x\mathrm{e}^{-x}\right)\)A1
\(f''(x)=(x-2)\mathrm{e}^{-x}\)AG
(c)
\(f''(2)=0\)A1
\(\mathrm{e}^{-x}\gt 0\) and \(x-2\) changes sign at \(x=2\), so \(f''\) changes sign (concavity changes)R1e.g. \(f''(1)=-\mathrm{e}^{-1}\lt 0\), \(f''(3)=\mathrm{e}^{-3}\gt 0\).
(d)
point \(\left(2,\ 2\mathrm{e}^{-2}\right)\)A1
gradient \(f'(2)=-\mathrm{e}^{-2}\)A1
\(y-2\mathrm{e}^{-2}=-\mathrm{e}^{-2}(x-2)\)A1Accept \(y=-\mathrm{e}^{-2}x+4\mathrm{e}^{-2}\).
(e)
\(x=4\)A1

Answers: (a) \((1-x)\mathrm{e}^{-x}\) · (d) \(y=-\mathrm{e}^{-2}x+4\mathrm{e}^{-2}\) · (e) \(x=4\)

57AASL5-q00805.9 Kinematics Paper 1Medium8 marks

A particle moves in a straight line. Its displacement, \(s\) metres, from a fixed point O after \(t\) seconds is given by \(s(t)=t^{3}-6t^{2}+9t\), for \(0\le t\le5\).

(a)

Find an expression for the velocity, \(v\), of the particle.

(1)
(b)

Find the values of \(t\) when the particle is at rest.

(2)
(c)

Find the total distance travelled by the particle in the 5 seconds.

(3)
(d)

Find the speed of the particle when its acceleration is zero.

(2)
Show mark scheme
WorkingMarkNotes
(a)
\(v=3t^{2}-12t+9\)A1
(b)
\(3(t-1)(t-3)=0\)M1
\(t=1,\ t=3\)A1
(c)
attempt to find \(s\) at \(t=0,1,3,5\): \(0,\ 4,\ 0,\ 20\)(M1)Or \(\int_{0}^{5}|v|\,\mathrm{d}t\) split at \(t=1\) and \(t=3\).
\(4+4+20\)(M1)Adding distances for the three stages.
\(28\) mA1
(d)
\(a=6t-12=0\Rightarrow t=2\)M1
\(v(2)=-3\), so speed \(=3\ \text{m s}^{-1}\)A1Award A0 for \(-3\).

Answers: (a) \(v=3t^{2}-12t+9\) · (b) \(t=1,\ 3\) · (c) 28 m · (d) \(3\ \text{m s}^{-1}\)

58AASL5-q00815.9 Kinematics Paper 1Medium8 marks

A particle moves in a straight line. Its acceleration, in m s−2, after \(t\) seconds is given by \(a(t)=4-2t\), for \(0\le t\le 6\). When \(t=0\) its velocity is \(5\ \text{m s}^{-1}\).

(a)

Find an expression for the velocity, \(v(t)\).

(3)
(b)

Find the value of \(t\) at which the particle changes direction.

(2)
(c)

Find the total distance travelled by the particle between \(t=0\) and \(t=6\).

(3)
Show mark scheme
WorkingMarkNotes
(a)
attempt to integrate \(a(t)\)M1
\(4t-t^{2}+c\)A1
\(v(t)=5+4t-t^{2}\)A1
(b)
\(5+4t-t^{2}=0\Rightarrow(5-t)(1+t)=0\)M1
\(t=5\)A1Must reject \(t=-1\). \(v\) changes sign at \(t=5\) since \(v(6)=-7\).
(c)
\(\displaystyle\int_{0}^{5}(5+4t-t^{2})\,\mathrm{d}t-\int_{5}^{6}(5+4t-t^{2})\,\mathrm{d}t\)M1Or \(\int_{0}^{6}|v|\,\mathrm{d}t\) split at their \(t\).
\(\dfrac{100}{3}\) and \(\dfrac{10}{3}\)A1Using \(5t+2t^{2}-\tfrac{t^{3}}{3}\): values \(\tfrac{100}{3}\) at \(t=5\) and \(30\) at \(t=6\).
\(\dfrac{110}{3}\) mA1Accept \(36\tfrac23\) m.

Answers: (a) \(v=5+4t-t^{2}\) · (b) \(t=5\) · (c) \(\tfrac{110}{3}\) m

59AASL5-q00835.9 Kinematics Paper 1Medium8 marks

A particle starts from a fixed point O and moves in a straight line. Its velocity, \(v\ \text{m s}^{-1}\), after \(t\) seconds is given by \(v(t)=4-\mathrm{e}^{t}\), for \(0\le t\le 2\).

(a)

Find the exact value of \(t\) at which the particle is instantaneously at rest.

(2)
(b)

Show that the displacement of the particle from O at this time is \(8\ln 2-3\) metres.

(3)
(c)

Find the exact total distance travelled by the particle in the 2 seconds.

(3)
Show mark scheme
WorkingMarkNotes
(a)
\(4-\mathrm{e}^{t}=0\)(M1)
\(t=\ln 4\)A1Accept \(2\ln 2\).
(b)
\(\displaystyle\int_{0}^{\ln 4}\left(4-\mathrm{e}^{t}\right)\mathrm{d}t\)M1
\(\left[4t-\mathrm{e}^{t}\right]_{0}^{\ln 4}\)A1
\((4\ln 4-4)-(0-1)=4\ln 4-3\)A1Must see \(\mathrm{e}^{\ln 4}=4\) used and \(4\ln 4=8\ln 2\).
\(=8\ln 2-3\)AG
(c)
displacement at \(t=2\): \(\displaystyle\int_{0}^{2}\left(4-\mathrm{e}^{t}\right)\mathrm{d}t=9-\mathrm{e}^{2}\); or \(\displaystyle\int_{\ln 4}^{2}\left(\mathrm{e}^{t}-4\right)\mathrm{d}t=\mathrm{e}^{2}-12+8\ln 2\)(M1)
distance \(=2(8\ln 2-3)-(9-\mathrm{e}^{2})\), or \((8\ln 2-3)+(\mathrm{e}^{2}-12+8\ln 2)\)(M1)Adding the two stages as positive quantities.
\(\mathrm{e}^{2}+16\ln 2-15\) mA1\(=3.479\ldots\) Accept equivalent exact forms, e.g. \(\mathrm{e}^{2}+8\ln 4-15\).

Answers: (a) \(t=\ln 4\) · (c) \(\mathrm{e}^{2}+16\ln 2-15\) m

60AASL5-q00845.9 Kinematics Paper 1Medium9 marks

A particle moves in a straight line, starting from a fixed point O. Its velocity, \(v\ \text{m s}^{-1}\), after \(t\) seconds is given by \(v(t)=3t^{2}-kt\), for \(0\le t\le 4\), where \(k\) is a positive constant. When \(t=4\) the particle is back at O.

(a)

Show that \(k=8\).

(2)
(b)

Find the value of \(t\), for \(0\lt t\lt 4\), at which the particle changes direction.

(2)
(c)

Find the total distance travelled by the particle in the 4 seconds.

(3)
(d)

Find the minimum velocity of the particle.

(2)
Show mark scheme
WorkingMarkNotes
(a)
\(\displaystyle\int_{0}^{4}(3t^{2}-kt)\,\mathrm{d}t=0\)M1Displacement after 4 seconds equated to zero.
\(\left[t^{3}-\tfrac{k}{2}t^{2}\right]_{0}^{4}=64-8k\)A1
\(64-8k=0\Rightarrow k=8\)AG
(b)
\(3t^{2}-8t=0\Rightarrow t(3t-8)=0\)(M1)
\(t=\dfrac{8}{3}\)A1Must reject \(t=0\).
(c)
\(\displaystyle\int_{0}^{8/3}(8t-3t^{2})\,\mathrm{d}t+\int_{8/3}^{4}(3t^{2}-8t)\,\mathrm{d}t\)(M1)Or \(2\times\left|\displaystyle\int_{0}^{8/3}(3t^{2}-8t)\,\mathrm{d}t\right|\), since the net displacement is zero.
each part equals \(\dfrac{256}{27}\)(A1)\(\left[4t^{2}-t^{3}\right]_{0}^{8/3}=\tfrac{256}{9}-\tfrac{512}{27}\)
\(\dfrac{512}{27}\) mA1Accept \(18\tfrac{26}{27}\) m.
(d)
\(a=6t-8=0\Rightarrow t=\tfrac{4}{3}\)(M1)
\(v_{\min}=-\dfrac{16}{3}\ \text{m s}^{-1}\)A1\(3\left(\tfrac{16}{9}\right)-8\left(\tfrac{4}{3}\right)\). Award A0 for \(\tfrac{16}{3}\) (that is the speed).

Answers: (b) \(t=\tfrac{8}{3}\) · (c) \(\tfrac{512}{27}\) m · (d) \(-\tfrac{16}{3}\ \text{m s}^{-1}\)

61AASL5-q00945.10 Indefinite integrals and reverse chain rule Paper 1Medium7 marks
(a)

Find \(\displaystyle\int\dfrac{x}{x^{2}+4}\,\mathrm{d}x\).

(3)
(b)

Hence find the exact value of \(\displaystyle\int_{0}^{2}\dfrac{x}{x^{2}+4}\,\mathrm{d}x\).

(2)
(c)

Find \(\displaystyle\int\sin x\cos^{3}x\,\mathrm{d}x\).

(2)
Show mark scheme
WorkingMarkNotes
(a)
recognizing \(2x\) as the derivative of \(x^{2}+4\), e.g. \(u=x^{2}+4,\ \mathrm{d}u=2x\,\mathrm{d}x\)M1
\(\displaystyle\int\dfrac{1}{2u}\,\mathrm{d}u\)A1Or \(k\ln(x^{2}+4)\) by inspection.
\(\tfrac{1}{2}\ln(x^{2}+4)+C\)A1
(b)
\(\tfrac12\ln8-\tfrac12\ln4\)M1Correct substitution of both limits into their answer to (a).
\(\tfrac12\ln2\)A1Accept \(\ln\sqrt2\).
(c)
\(u=\cos x,\ \mathrm{d}u=-\sin x\,\mathrm{d}x\), or \(k\cos^{4}x\) by inspectionM1
\(-\tfrac14\cos^{4}x+C\)A1

Answers: (a) \(\tfrac12\ln(x^{2}+4)+C\) · (b) \(\tfrac12\ln2\) · (c) \(-\tfrac14\cos^{4}x+C\)

62AASL5-q00995.10 Indefinite integrals and reverse chain rule Paper 1Medium5 marks
(a)

Find \(\displaystyle\int x^{2}\left(x^{3}+1\right)^{5}\mathrm{d}x\).

(3)
(b)

Hence find the value of \(\displaystyle\int_{0}^{1}x^{2}\left(x^{3}+1\right)^{5}\mathrm{d}x\).

(2)
Show mark scheme
WorkingMarkNotes
(a)
recognizing \(x^{2}\) as a multiple of the derivative of \(x^{3}+1\), or substitution \(u=x^{3}+1\), \(\mathrm{d}u=3x^{2}\,\mathrm{d}x\)M1
\((x^{3}+1)^{6}\) seen, or \(\displaystyle\int\tfrac13u^{5}\,\mathrm{d}u\)A1
\(\dfrac{1}{18}\left(x^{3}+1\right)^{6}+C\)A1
(b)
\(\dfrac{2^{6}}{18}-\dfrac{1}{18}\)(M1)Substituting both limits into their (a).
\(\dfrac{7}{2}\)A1Accept \(\tfrac{63}{18}\).

Answers: (a) \(\tfrac{1}{18}(x^{3}+1)^{6}+C\) · (b) \(\tfrac72\)

63AASL5-q01005.10 Indefinite integrals and reverse chain rule Paper 1Medium5 marks
(a)

By using the substitution \(u=\cos x\), find \(\displaystyle\int\sin x\,\mathrm{e}^{\cos x}\,\mathrm{d}x\).

(3)
(b)

Hence find the exact value of \(\displaystyle\int_{0}^{\frac{\pi}{2}}\sin x\,\mathrm{e}^{\cos x}\,\mathrm{d}x\).

(2)
Show mark scheme
WorkingMarkNotes
(a)
\(\dfrac{\mathrm{d}u}{\mathrm{d}x}=-\sin x\), so the integral becomes \(\displaystyle\int-\mathrm{e}^{u}\,\mathrm{d}u\)M1
\(-\mathrm{e}^{u}\)A1
\(-\mathrm{e}^{\cos x}+C\)A1Must be in terms of x.
(b)
\(-\mathrm{e}^{\cos(\pi/2)}-\left(-\mathrm{e}^{\cos 0}\right)=-\mathrm{e}^{0}+\mathrm{e}^{1}\)(M1)
\(\mathrm{e}-1\)A1

Answers: (a) \(-\mathrm{e}^{\cos x}+C\) · (b) \(\mathrm{e}-1\)

64AASL5-q01015.10 Indefinite integrals and reverse chain rule Paper 1Medium6 marks
(a)

Find \(\displaystyle\int\dfrac{\cos x}{3+\sin x}\,\mathrm{d}x\).

(2)
(b)

By writing \(\tan x=\dfrac{\sin x}{\cos x}\), find \(\displaystyle\int\tan x\,\mathrm{d}x\), for \(0\le x\lt\dfrac{\pi}{2}\).

(2)
(c)

Hence find the exact value of \(\displaystyle\int_{0}^{\frac{\pi}{3}}\tan x\,\mathrm{d}x\).

(2)
Show mark scheme
WorkingMarkNotes
(a)
recognizing the numerator as the derivative of the denominator, or \(u=3+\sin x\)(M1)
\(\ln(3+\sin x)+C\)A1Accept \(\ln|3+\sin x|\).
(b)
numerator is \(-1\times\) the derivative of \(\cos x\)(M1)
\(-\ln(\cos x)+C\)A1Accept \(-\ln|\cos x|+C\) or \(\ln(\sec x)+C\).
(c)
\(-\ln\left(\cos\tfrac{\pi}{3}\right)+\ln(\cos 0)=-\ln\tfrac12+0\)(M1)
\(\ln 2\)A1

Answers: (a) \(\ln(3+\sin x)+C\) · (b) \(-\ln(\cos x)+C\) · (c) \(\ln 2\)

65AASL5-q01025.10 Indefinite integrals and reverse chain rule Paper 1Medium9 marks

A function \(f\) satisfies \(f''(x)=8\mathrm{e}^{2x}\), for \(x\in\mathbb{R}\). The gradient of the graph of \(f\) at the point \((0,\,-1)\) is 3.

(a)

Find \(f'(x)\).

(3)
(b)

Find \(f(x)\).

(3)
(c)

Find the exact coordinates of the stationary point on the graph of \(f\) and justify that it is a minimum.

(3)
Show mark scheme
WorkingMarkNotes
(a)
attempt to integrate \(f''(x)\)M1
\(4\mathrm{e}^{2x}+c\)A1
\(4+c=3\Rightarrow f'(x)=4\mathrm{e}^{2x}-1\)A1
(b)
attempt to integrate their \(f'(x)\)M1
\(2\mathrm{e}^{2x}-x+d\)A1FT from (a).
\(2+d=-1\Rightarrow f(x)=2\mathrm{e}^{2x}-x-3\)A1
(c)
\(4\mathrm{e}^{2x}=1\Rightarrow x=-\ln 2\)A1Accept \(\tfrac12\ln\tfrac14\).
\(y=2\left(\tfrac14\right)+\ln 2-3=\ln 2-\dfrac52\)A1
\(f''(x)=8\mathrm{e}^{2x}\gt 0\) for all \(x\), so it is a minimumR1

Answers: (a) \(f'(x)=4\mathrm{e}^{2x}-1\) · (b) \(f(x)=2\mathrm{e}^{2x}-x-3\) · (c) \(\left(-\ln 2,\ \ln 2-\tfrac52\right)\)

66AASL5-q01065.11 Definite integrals and areas Paper 1Medium8 marks

Let \(f(x)=x^{3}-2x^{2}-3x\). The diagram shows part of the graph of \(f\). The shaded region A lies above the \(x\)-axis and the shaded region B lies below the \(x\)-axis.

xyOABy = f(x)
(a)

Find the \(x\)-coordinates of the points where the graph of \(f\) meets the \(x\)-axis.

(2)
(b)

Find the area of region A.

(2)
(c)

Find the area of region B.

(3)
(d)

Hence write down the value of \(\displaystyle\int_{-1}^{3}f(x)\,\mathrm{d}x\).

(1)
Show mark scheme
WorkingMarkNotes
(a)
\(x(x^{2}-2x-3)=0\Rightarrow x(x+1)(x-3)=0\)M1
\(x=-1,\ 0,\ 3\)A1
(b)
\(\left[\tfrac{x^{4}}{4}-\tfrac{2x^{3}}{3}-\tfrac{3x^{2}}{2}\right]_{-1}^{0}=0-\left(\tfrac14+\tfrac23-\tfrac32\right)\)M1Correct integration and substitution of limits.
\(\dfrac{7}{12}\)A1
(c)
\(\displaystyle\int_{0}^{3}f(x)\,\mathrm{d}x=\tfrac{81}{4}-18-\tfrac{27}{2}\)M1
\(=-\dfrac{45}{4}\)A1
area \(=\dfrac{45}{4}\)A1Award A1 for the positive value.
(d)
\(\dfrac{7}{12}-\dfrac{45}{4}=-\dfrac{32}{3}\)A1FT from (b) and (c).

Answers: (a) \(-1,\ 0,\ 3\) · (b) \(\tfrac{7}{12}\) · (c) \(\tfrac{45}{4}\) · (d) \(-\tfrac{32}{3}\)

67AASL5-q01105.11 Definite integrals and areas Paper 1Medium6 marks

The diagram shows the graphs of \(y=5-x\) and \(y=\dfrac{4}{x}\), for \(x\gt 0\). The shaded region R is enclosed by the two graphs.

xyO145y = 5 − xy = 4/xR
(a)

Show that the graphs intersect where \(x=1\) and \(x=4\).

(2)
(b)

Find the exact area of R. Give your answer in the form \(p-q\ln 2\), where \(p,q\in\mathbb{Q}\).

(4)
Show mark scheme
WorkingMarkNotes
(a)
\(5-x=\dfrac{4}{x}\Rightarrow x^{2}-5x+4=0\)M1
\((x-1)(x-4)=0\)A1
\(x=1,\ x=4\)AG
(b)
\(\displaystyle\int_{1}^{4}\left(5-x-\dfrac{4}{x}\right)\mathrm{d}x\)M1Correct expression, including limits, must be seen. Accept the integral of the difference in the opposite order with the modulus taken.
\(\left[5x-\dfrac{x^{2}}{2}-4\ln x\right]_{1}^{4}\)A1
\((20-8-4\ln 4)-\left(5-\tfrac12-0\right)\)M1Substituting both limits.
\(\dfrac{15}{2}-8\ln 2\)A1\(=1.95\ldots\) Accept \(p=\tfrac{15}{2},\ q=8\).

Answers: (b) \(\tfrac{15}{2}-8\ln 2\)

68AASL5-q01125.11 Definite integrals and areas Paper 1Medium7 marks

Let \(f(x)=\sin(2x)\), for \(0\le x\le\dfrac{2\pi}{3}\).

(a)

Find the value of \(x\), for \(0\lt x\lt\dfrac{2\pi}{3}\), at which the graph of \(f\) meets the \(x\)-axis.

(1)
(b)

Find the value of \(\displaystyle\int_{0}^{\frac{2\pi}{3}}f(x)\,\mathrm{d}x\).

(2)
(c)

Find the total area of the region enclosed by the graph of \(f\), the \(x\)-axis and the line \(x=\dfrac{2\pi}{3}\).

(3)
(d)

Explain why the answers to parts (b) and (c) are different.

(1)
Show mark scheme
WorkingMarkNotes
(a)
\(x=\dfrac{\pi}{2}\)A1
(b)
\(\left[-\tfrac12\cos(2x)\right]_{0}^{2\pi/3}=-\tfrac12\cos\tfrac{4\pi}{3}+\tfrac12\cos 0=\tfrac14+\tfrac12\)(M1)
\(\dfrac34\)A1
(c)
\(\displaystyle\int_{0}^{\pi/2}\sin(2x)\,\mathrm{d}x+\left|\displaystyle\int_{\pi/2}^{2\pi/3}\sin(2x)\,\mathrm{d}x\right|\)M1Correct expression for the area must be seen; FT from their (a).
\(1\) and \(\left|-\tfrac14\right|=\tfrac14\)A1
\(\dfrac54\)A1
(d)
between \(\tfrac{\pi}{2}\) and \(\tfrac{2\pi}{3}\) the curve is below the \(x\)-axis, so that part contributes a negative value to the integral but a positive value to the areaR1

Answers: (a) \(\tfrac{\pi}{2}\) · (b) \(\tfrac34\) · (c) \(\tfrac54\)

69AASL5-q00145.2 Increasing and decreasing functions Paper 1Hard10 marks

Let \(f(x)=x^{3}-kx^{2}+12x+1\), where \(k\in\mathbb{R}\).

(a)

Find \(f'(x)\).

(1)
(b)

Find the set of values of \(k\) for which \(f'(x)\gt 0\) for all \(x\in\mathbb{R}\).

(4)
(c)

Let \(k=6\). Find the coordinates of the point on the graph of \(f\) where the gradient is zero.

(2)
(d)

Let \(k=7\). Find the interval on which \(f\) is decreasing. Give the endpoints in the form \(\dfrac{a\pm\sqrt{b}}{3}\), where \(a,b\in\mathbb{Z}\).

(3)
Show mark scheme
WorkingMarkNotes
(a)
\(3x^{2}-2kx+12\)A1
(b)
recognizing that the quadratic \(f'(x)\) has no real roots: discriminant \(\lt 0\)M1
\((-2k)^{2}-4(3)(12)\lt 0\), i.e. \(4k^{2}-144\lt 0\)A1
\(k^{2}\lt 36\) or critical values \(k=\pm6\)M1
\(-6\lt k\lt 6\)A1Award A0 for \(-6\le k\le 6\) (when \(k=\pm6\), \(f'\) has a zero).
(c)
\(3x^{2}-12x+12=3(x-2)^{2}=0\Rightarrow x=2\)(M1)
\((2,\,9)\)A1\(f(2)=8-24+24+1=9\)
(d)
\(3x^{2}-14x+12\lt 0\), attempting the quadratic formulaM1
\(x=\dfrac{14\pm\sqrt{52}}{6}=\dfrac{7\pm\sqrt{13}}{3}\)A1
\(\dfrac{7-\sqrt{13}}{3}\lt x\lt \dfrac{7+\sqrt{13}}{3}\)A1Accept non-strict inequalities.

Answers: (a) \(3x^{2}-2kx+12\) · (b) \(-6\lt k\lt 6\) · (c) \((2,\,9)\) · (d) \(\frac{7-\sqrt{13}}{3}\lt x\lt\frac{7+\sqrt{13}}{3}\)

70AASL5-q00155.2 Increasing and decreasing functions Paper 1Hard9 marks

A function \(f\) has derivative \(f'(x)=(x+2)(x-1)(x-5)\), for \(x\in\mathbb{R}\).

(a)

Find the intervals on which \(f\) is decreasing.

(3)
(b)

Show that \(f'(x)=x^{3}-4x^{2}-7x+10\), and hence find an expression for \(f(x)\) in terms of \(x\) and a constant of integration \(c\).

(3)
(c)

The graph of \(f\) has two local minimum points. Determine which of these is the lower point.

(3)
Show mark scheme
WorkingMarkNotes
(a)
considering the sign of \(f'(x)\) in each interval (sign diagram or graph of the cubic)M1
\(x\lt -2\)A1
\(1\lt x\lt 5\)A1Accept non-strict inequalities.
(b)
\((x^{2}+x-2)(x-5)=x^{3}-5x^{2}+x^{2}-5x-2x+10\), so \(f'(x)=x^{3}-4x^{2}-7x+10\)A1
attempting to anti-differentiate (power increased by one in at least two terms)M1
\(f(x)=\dfrac{x^{4}}{4}-\dfrac{4x^{3}}{3}-\dfrac{7x^{2}}{2}+10x+c\)A1
(c)
local minima at \(x=-2\) and \(x=5\) (\(f'\) changes from negative to positive)R1
\(f(-2)=-\dfrac{58}{3}+c\) and \(f(5)=-\dfrac{575}{12}+c\)A1Or \(f(5)-f(-2)=-\dfrac{343}{12}\).
\(f(5)\lt f(-2)\), so the local minimum at \(x=5\) is lowerA1Award A1 only if correct values (or difference) are seen.

Answers: (a) \(x\lt -2\), \(1\lt x\lt 5\) · (b) \(\frac{x^{4}}{4}-\frac{4x^{3}}{3}-\frac{7x^{2}}{2}+10x+c\) · (c) the minimum at \(x=5\)

71AASL5-q00235.3 Differentiating polynomials and integer powers Paper 1Hard9 marks

Let \(f(x)=ax^{n}\), where \(a\neq0\), \(n\in\mathbb{Z}\) and \(x\gt 0\). It is given that \(f(2)=24\) and \(f'(2)=-36\).

(a)

Show that \(x\,f'(x)=n\,f(x)\) for all \(x\gt 0\).

(2)
(b)

Hence find the value of \(n\).

(2)
(c)

Find the value of \(a\).

(2)
(d)

Find the value of \(x\) for which \(f'(x)=-\dfrac{9}{4}\).

(3)
Show mark scheme
WorkingMarkNotes
(a)
\(f'(x)=anx^{n-1}\)M1
\(x\,f'(x)=anx^{n}=n\,(ax^{n})\)A1
\(=n\,f(x)\)AG
(b)
\(2(-36)=24n\)M1Must use the result from (a) with \(x=2\).
\(n=-3\)A1
(c)
\(a(2)^{-3}=24\)(M1)
\(a=192\)A1
(d)
\(f'(x)=-576x^{-4}=-\dfrac{9}{4}\)M1FT from their \(a\) and \(n\).
\(x^{4}=256\)A1
\(x=4\)A1Award A0 if \(x=-4\) is also given (\(x\gt 0\)).

Answers: (b) \(n=-3\) · (c) \(a=192\) · (d) \(x=4\)

72AASL5-q00275.4 Tangents and normals Paper 1Hard7 marks

The point \(\text{A}(a,\,a^{2})\) lies on the curve \(y=x^{2}\).

(a)

Show that the equation of the tangent to the curve at A is \(y=2ax-a^{2}\).

(2)
(b)

The tangent at A passes through the point \((1,\,-3)\). Show that \(a^{2}-2a-3=0\).

(1)
(c)

Hence find the equations of the two tangents to \(y=x^{2}\) that pass through the point \((1,\,-3)\).

(4)
Show mark scheme
WorkingMarkNotes
(a)
gradient \(=2a\) and \(y-a^{2}=2a(x-a)\)M1
\(y=2ax-2a^{2}+a^{2}\)A1
\(y=2ax-a^{2}\)AG
(b)
\(-3=2a(1)-a^{2}\), so \(a^{2}-2a-3=0\)A1
(c)
\((a-3)(a+1)=0\)M1
\(a=3,\ a=-1\)A1
\(y=6x-9\)A1
\(y=-2x-1\)A1

Answers: (c) \(y=6x-9\) and \(y=-2x-1\)

73AASL5-q00325.4 Tangents and normals Paper 1Hard14 marks

Let \(f(x)=x^{3}-6x^{2}+9x+1\), for \(x\in\mathbb{R}\).

(a)

Find \(f'(x)\).

(2)
(b)

Find the intervals on which \(f\) is increasing and the interval on which \(f\) is decreasing.

(4)
(c)(i)

The line \(L\) is the tangent to the graph of \(f\) at the point where \(x=0\).

Find the equation of \(L\).

(2)
(c)(ii)

\(L\) meets the graph of \(f\) again at the point B. Find the coordinates of B.

(3)
(d)

Find the equation of the normal to the graph of \(f\) at the point where \(x=2\). Give your answer in the form \(y=mx+c\).

(3)
Show mark scheme
WorkingMarkNotes
(a)
\(3x^{2}-12x\)A1Award for any two correct terms.
\(f'(x)=3x^{2}-12x+9\)A1
(b)
\(3x^{2}-12x+9=0\)M1
\(3(x-1)(x-3)=0\Rightarrow x=1,\ x=3\)A1
increasing for \(x\lt 1\) and \(x\gt 3\)A1
decreasing for \(1\lt x\lt 3\)A1Accept non-strict inequalities.
(c)(i)
\(f(0)=1\) and \(f'(0)=9\)(A1)
\(y=9x+1\)A1
(c)(ii)
\(x^{3}-6x^{2}+9x+1=9x+1\)M1
\(x^{2}(x-6)=0\Rightarrow x=6\)A1
\(\text{B}(6,\,55)\)A1
(d)
\(f(2)=3\) and \(f'(2)=-3\)(A1)
gradient of normal \(=\dfrac{1}{3}\): \(y-3=\dfrac{1}{3}(x-2)\)(M1)
\(y=\dfrac{1}{3}x+\dfrac{7}{3}\)A1

Answers: (a) \(3x^{2}-12x+9\) · (b) increasing \(x\lt1\), \(x\gt3\); decreasing \(1\lt x\lt3\) · (c)(i) \(y=9x+1\) (ii) \(\text{B}(6,\,55)\) · (d) \(y=\frac13x+\frac73\)

74AASL5-q00435.6 Differentiation rules Paper 1Hard8 marks

Let \(g(x)=\dfrac{\sin x}{2+\cos x}\), for \(0\le x\le 2\pi\).

(a)

Show that \(g'(x)=\dfrac{2\cos x+1}{(2+\cos x)^{2}}\).

(3)
(b)

Find the \(x\)-coordinates of the stationary points on the graph of \(g\).

(3)
(c)

Find the maximum value of \(g(x)\).

(2)
Show mark scheme
WorkingMarkNotes
(a)
attempt to use the quotient rule: \(\dfrac{(2+\cos x)\cos x-\sin x(-\sin x)}{(2+\cos x)^{2}}\)M1Award M1 for an attempt with the terms in the correct order in the numerator.
\(\dfrac{2\cos x+\cos^{2}x+\sin^{2}x}{(2+\cos x)^{2}}\)A1
using \(\cos^{2}x+\sin^{2}x=1\)A1
\(g'(x)=\dfrac{2\cos x+1}{(2+\cos x)^{2}}\)AG
(b)
\(2\cos x+1=0\Rightarrow\cos x=-\tfrac12\)M1
\(x=\dfrac{2\pi}{3}\)A1
\(x=\dfrac{4\pi}{3}\)A1Award A1A0 for answers in degrees.
(c)
\(g\left(\tfrac{2\pi}{3}\right)=\dfrac{\frac{\sqrt3}{2}}{2-\frac12}\)(M1)Award for substituting their \(x\) at which \(\sin x\gt 0\). Note \(g(0)=g(2\pi)=0\) and \(g\left(\tfrac{4\pi}{3}\right)\lt 0\).
\(\dfrac{\sqrt3}{3}\)A1Accept \(\dfrac{1}{\sqrt3}\).

Answers: (b) \(x=\dfrac{2\pi}{3},\ \dfrac{4\pi}{3}\) · (c) \(\dfrac{\sqrt3}{3}\)

75AASL5-q00525.6 Differentiation rules Paper 1Hard10 marks

A curve has equation \(y=\dfrac{1+\sin x}{\cos x}\), for \(-\dfrac{\pi}{2}\lt x\lt\dfrac{\pi}{2}\).

(a)

Show that \(\dfrac{\mathrm{d}y}{\mathrm{d}x}=\dfrac{1}{1-\sin x}\).

(4)
(b)

Find the gradient of the curve at \(x=\dfrac{\pi}{6}\).

(1)
(c)

Find the value of \(x\) at which the gradient of the curve is \(\dfrac23\).

(3)
(d)

Explain why the gradient of the curve is always greater than \(\dfrac12\).

(2)
Show mark scheme
WorkingMarkNotes
(a)
attempt to use the quotient rule: \(\dfrac{\cos x\cos x-(1+\sin x)(-\sin x)}{\cos^{2}x}\)M1
\(\dfrac{\cos^{2}x+\sin x+\sin^{2}x}{\cos^{2}x}=\dfrac{1+\sin x}{\cos^{2}x}\)A1Using \(\sin^{2}x+\cos^{2}x=1\).
\(\cos^{2}x=1-\sin^{2}x=(1-\sin x)(1+\sin x)\)M1
\(\dfrac{1+\sin x}{(1-\sin x)(1+\sin x)}\), with \(1+\sin x\neq0\) cancelledA1
\(\dfrac{\mathrm{d}y}{\mathrm{d}x}=\dfrac{1}{1-\sin x}\)AG
(b)
\(\dfrac{1}{1-\frac12}=2\)A1
(c)
\(\dfrac{1}{1-\sin x}=\dfrac23\Rightarrow1-\sin x=\dfrac32\)M1
\(\sin x=-\dfrac12\)A1
\(x=-\dfrac{\pi}{6}\)A1Award A0 if additional values outside the domain are given.
(d)
on the domain \(-1\lt\sin x\lt1\), so \(0\lt1-\sin x\lt2\)R1
so \(\dfrac{1}{1-\sin x}\gt\dfrac12\)R1Must refer to taking the reciprocal of a positive quantity less than 2.

Answers: (b) \(2\) · (c) \(x=-\dfrac{\pi}{6}\)

76AASL5-q00555.6 Differentiation rules Paper 1Hard14 marks

Let \(f(x)=\mathrm{e}^{\sin x}\), for \(0\le x\le2\pi\).

(a)

Find \(f'(x)\).

(2)
(b)

Find the coordinates of the stationary points on the graph of \(f\).

(4)
(c)

Show that \(f''(x)=\mathrm{e}^{\sin x}\left(\cos^{2}x-\sin x\right)\).

(2)
(d)

Hence show that, at a point of inflexion, \(\sin^{2}x+\sin x-1=0\).

(2)
(e)

Hence find the exact value of \(\sin x\) at the points of inflexion, justifying your answer.

(3)
(f)

Write down the number of points of inflexion on the graph of \(f\).

(1)
Show mark scheme
WorkingMarkNotes
(a)
attempt to use the chain ruleM1
\(f'(x)=\cos x\,\mathrm{e}^{\sin x}\)A1
(b)
\(\cos x\,\mathrm{e}^{\sin x}=0\Rightarrow\cos x=0\), since \(\mathrm{e}^{\sin x}\gt 0\)M1
\(x=\dfrac{\pi}{2},\ \dfrac{3\pi}{2}\)A1
\(\left(\dfrac{\pi}{2},\ \mathrm{e}\right)\)A1
\(\left(\dfrac{3\pi}{2},\ \mathrm{e}^{-1}\right)\)A1Accept \(\dfrac{1}{\mathrm{e}}\).
(c)
attempt to use the product rule on \(\cos x\,\mathrm{e}^{\sin x}\)M1
\(-\sin x\,\mathrm{e}^{\sin x}+\cos x\times\cos x\,\mathrm{e}^{\sin x}\)A1
\(f''(x)=\mathrm{e}^{\sin x}\left(\cos^{2}x-\sin x\right)\)AG
(d)
\(f''(x)=0\Rightarrow\cos^{2}x-\sin x=0\) and use of \(\cos^{2}x=1-\sin^{2}x\)M1
\(1-\sin^{2}x-\sin x=0\)A1
\(\sin^{2}x+\sin x-1=0\)AG
(e)
attempt to solve the quadratic in \(\sin x\), e.g. quadratic formulaM1
\(\sin x=\dfrac{-1\pm\sqrt5}{2}\)A1
\(\dfrac{-1-\sqrt5}{2}\lt -1\) is impossible, so \(\sin x=\dfrac{\sqrt5-1}{2}\)R1
(f)
\(2\)A1\(\sin x=0.618\ldots\) has two solutions in \([0,\,2\pi]\), both in \(\left(0,\,\pi\right)\), and \(f''\) changes sign at each.

Answers: (a) \(\cos x\,\mathrm{e}^{\sin x}\) · (b) \(\left(\tfrac{\pi}{2},\mathrm{e}\right)\), \(\left(\tfrac{3\pi}{2},\mathrm{e}^{-1}\right)\) · (e) \(\sin x=\dfrac{\sqrt5-1}{2}\) · (f) 2

77AASL5-q00635.7 The second derivative and graphs Paper 1Hard8 marks

Let \(f(x)=\mathrm{e}^{x}+\mathrm{e}^{-2x}\), for \(x\in\mathbb{R}\).

(a)

Find \(f'(x)\) and \(f''(x)\).

(2)
(b)

Show that the graph of \(f\) is concave-up for all values of \(x\).

(1)
(c)

Hence explain why the graph of \(f\) has at most one stationary point.

(1)
(d)

Find the exact \(x\)-coordinate of the stationary point.

(2)
(e)

Show that the minimum value of \(f\) is \(\dfrac{3}{\sqrt[3]{4}}\).

(2)
Show mark scheme
WorkingMarkNotes
(a)
\(f'(x)=\mathrm{e}^{x}-2\mathrm{e}^{-2x}\)A1
\(f''(x)=\mathrm{e}^{x}+4\mathrm{e}^{-2x}\)A1
(b)
\(\mathrm{e}^{x}\gt 0\) and \(4\mathrm{e}^{-2x}\gt 0\), so \(f''(x)\gt 0\) for all \(x\)R1
concave-up for all \(x\)AG
(c)
\(f''\gt 0\) so \(f'\) is (strictly) increasing; hence \(f'(x)=0\) for at most one value of \(x\)R1
(d)
\(\mathrm{e}^{x}=2\mathrm{e}^{-2x}\Rightarrow\mathrm{e}^{3x}=2\)M1
\(x=\dfrac{\ln2}{3}\)A1Accept \(\ln\sqrt[3]{2}\).
(e)
\(f\left(\tfrac{\ln2}{3}\right)=2^{\frac13}+2^{-\frac23}\)M1
\(=2^{-\frac23}(2+1)=\dfrac{3}{2^{\frac23}}\)A1Minimum since \(f''\gt 0\).
\(\dfrac{3}{\sqrt[3]{4}}\)AG

Answers: (a) \(f'=\mathrm{e}^{x}-2\mathrm{e}^{-2x}\), \(f''=\mathrm{e}^{x}+4\mathrm{e}^{-2x}\) · (d) \(x=\dfrac{\ln2}{3}\)

78AASL5-q00645.7 The second derivative and graphs Paper 1Hard10 marks

Let \(f(x)=\sin x+kx^{2}\), where \(k\in\mathbb{R}\) and \(x\in\mathbb{R}\).

(a)

Find \(f'(x)\) and \(f''(x)\).

(2)
(b)

Find the set of values of \(k\) for which \(f''(x)\gt 0\) for all values of \(x\).

(3)
(c)

Let \(k=\dfrac14\). Find the \(x\)-coordinates of the points of inflexion on the graph of \(f\) for \(0\le x\le2\pi\).

(3)
(d)

Let \(k=\dfrac14\). Find the exact gradient of the graph of \(f\) at the point of inflexion with the larger \(x\)-coordinate.

(2)
Show mark scheme
WorkingMarkNotes
(a)
\(f'(x)=\cos x+2kx\)A1
\(f''(x)=-\sin x+2k\)A1
(b)
\(2k-\sin x\gt 0\) for all \(x\)M1
the greatest value of \(\sin x\) is 1, so need \(2k\gt 1\)R1
\(k\gt\dfrac12\)A1Award A0 for \(k\ge\tfrac12\): when \(k=\tfrac12\), \(f''\left(\tfrac{\pi}{2}\right)=0\).
(c)
\(\tfrac12-\sin x=0\Rightarrow\sin x=\tfrac12\)M1
\(x=\dfrac{\pi}{6}\)A1\(f''\) changes sign at each value since \(\cos x\neq0\) there.
\(x=\dfrac{5\pi}{6}\)A1
(d)
\(f'\left(\tfrac{5\pi}{6}\right)=\cos\left(\tfrac{5\pi}{6}\right)+\tfrac12\times\tfrac{5\pi}{6}\)(M1)
\(\dfrac{5\pi}{12}-\dfrac{\sqrt3}{2}\)A1

Answers: (b) \(k\gt\tfrac12\) · (c) \(x=\dfrac{\pi}{6},\ \dfrac{5\pi}{6}\) · (d) \(\dfrac{5\pi}{12}-\dfrac{\sqrt3}{2}\)

79AASL5-q00725.8 Stationary points, inflexion and optimization Paper 1Hard11 marks

The point \(\text{P}\left(a,\,\mathrm{e}^{-a}\right)\), where \(a\ge0\), lies on the curve \(y=\mathrm{e}^{-x}\). The line L is the tangent to the curve at P. The triangle formed by L and the coordinate axes is shaded in the diagram.

xyOPy = e−xL
Diagram not to scale
(a)

Show that the equation of L is \(y=-\mathrm{e}^{-a}x+(a+1)\mathrm{e}^{-a}\).

(2)
(b)

Find, in terms of \(a\), the coordinates of the points where L meets the \(x\)-axis and the \(y\)-axis.

(2)
(c)

Hence show that the area of the shaded triangle is \(T=\dfrac12(a+1)^{2}\mathrm{e}^{-a}\).

(1)
(d)

Find \(\dfrac{\mathrm{d}T}{\mathrm{d}a}\).

(2)
(e)

Find the exact maximum value of \(T\), justifying that it is a maximum.

(4)
Show mark scheme
WorkingMarkNotes
(a)
gradient of L \(=-\mathrm{e}^{-a}\)A1
\(y-\mathrm{e}^{-a}=-\mathrm{e}^{-a}(x-a)\)M1
\(y=-\mathrm{e}^{-a}x+(a+1)\mathrm{e}^{-a}\)AG
(b)
\(\big(a+1,\ 0\big)\)A1
\(\big(0,\ (a+1)\mathrm{e}^{-a}\big)\)A1
(c)
\(T=\tfrac12\times(a+1)\times(a+1)\mathrm{e}^{-a}\)A1
\(T=\dfrac12(a+1)^{2}\mathrm{e}^{-a}\)AG
(d)
attempt to use the product ruleM1
\(\dfrac{\mathrm{d}T}{\mathrm{d}a}=(a+1)\mathrm{e}^{-a}-\tfrac12(a+1)^{2}\mathrm{e}^{-a}\)A1Accept \(\tfrac12(a+1)(1-a)\mathrm{e}^{-a}\).
(e)
\(\tfrac12(a+1)(1-a)\mathrm{e}^{-a}=0\)M1
\(a=1\)A1Reject \(a=-1\) since \(a\ge0\).
\(\dfrac{\mathrm{d}T}{\mathrm{d}a}\gt 0\) for \(0\le a\lt1\) and \(\dfrac{\mathrm{d}T}{\mathrm{d}a}\lt 0\) for \(a\gt1\), so a maximumR1
\(T=\dfrac{2}{\mathrm{e}}\)A1\(\tfrac12(2)^{2}\mathrm{e}^{-1}\).

Answers: (b) \((a+1,0)\), \(\left(0,(a+1)\mathrm{e}^{-a}\right)\) · (d) \(\tfrac12(a+1)(1-a)\mathrm{e}^{-a}\) · (e) \(\dfrac{2}{\mathrm{e}}\) at \(a=1\)

80AASL5-q00955.10 Indefinite integrals and reverse chain rule Paper 1Hard8 marks

Let \(f(x)=\dfrac{\ln x}{x}\), for \(x\gt 0\).

(a)

Show that \(\dfrac{\mathrm{d}}{\mathrm{d}x}\big((\ln x)^{2}\big)=2f(x)\).

(2)
(b)

Hence find \(\displaystyle\int_{1}^{\mathrm{e}^{2}}f(x)\,\mathrm{d}x\).

(2)
(c)

Find the area of the region enclosed by the graph of \(f\), the \(x\)-axis and the lines \(x=\mathrm{e}^{-1}\) and \(x=\mathrm{e}\).

(4)
Show mark scheme
WorkingMarkNotes
(a)
attempt to use the chain rule: \(2\ln x\times\dfrac{\mathrm{d}}{\mathrm{d}x}(\ln x)\)M1
\(2\ln x\times\dfrac{1}{x}=\dfrac{2\ln x}{x}\)A1
\(=2f(x)\)AG
(b)
\(\left[\tfrac12(\ln x)^{2}\right]_{1}^{\mathrm{e}^{2}}=\tfrac12(2)^{2}-\tfrac12(0)^{2}\)M1
\(2\)A1
(c)
\(f(x)\lt 0\) for \(\mathrm{e}^{-1}\lt x\lt 1\) and \(f(x)\gt 0\) for \(1\lt x\lt\mathrm{e}\), so the integral is split at \(x=1\)R1
\(\displaystyle\int_{\mathrm{e}^{-1}}^{1}f(x)\,\mathrm{d}x=0-\tfrac12(-1)^{2}=-\tfrac12\)A1
\(\displaystyle\int_{1}^{\mathrm{e}}f(x)\,\mathrm{d}x=\tfrac12\)A1
area \(=\tfrac12+\tfrac12=1\)A1Award A0 for an answer of 0 (from \(\int_{\mathrm{e}^{-1}}^{\mathrm{e}}f\)).

Answers: (b) \(2\) · (c) \(1\)

81AASL5-q01035.10 Indefinite integrals and reverse chain rule Paper 1Hard8 marks
(a)

Show that \(\sin^{3}x=\sin x-\sin x\cos^{2}x\).

(1)
(b)

Hence find \(\displaystyle\int\sin^{3}x\,\mathrm{d}x\).

(3)
(c)

Find the exact value of \(\displaystyle\int_{0}^{\pi}\sin^{3}x\,\mathrm{d}x\).

(2)
(d)

Without further integration, write down the value of \(\displaystyle\int_{0}^{2\pi}\sin^{3}x\,\mathrm{d}x\). Justify your answer.

(2)
Show mark scheme
WorkingMarkNotes
(a)
\(\sin^{3}x=\sin x\left(1-\cos^{2}x\right)\)M1Use of \(\sin^{2}x=1-\cos^{2}x\).
\(=\sin x-\sin x\cos^{2}x\)AG
(b)
\(\displaystyle\int\sin x\,\mathrm{d}x=-\cos x\)A1
recognizing \(\sin x\cos^{2}x\) as a multiple of \(f'(x)f(x)^{2}\) with \(f(x)=\cos x\), or \(u=\cos x\)M1
\(-\cos x+\dfrac{1}{3}\cos^{3}x+C\)A1
(c)
\(\left(1-\tfrac13\right)-\left(-1+\tfrac13\right)\)(M1)
\(\dfrac{4}{3}\)A1
(d)
\(0\)A1
\(\sin^{3}(x+\pi)=-\sin^{3}x\), so the part of the graph from \(\pi\) to \(2\pi\) is below the axis with the same area as the part from \(0\) to \(\pi\)R1Accept \(\int_{\pi}^{2\pi}\sin^{3}x\,\mathrm{d}x=-\tfrac43\) found by symmetry or by their (b). Do not award A1R0.

Answers: (b) \(-\cos x+\tfrac13\cos^{3}x+C\) · (c) \(\tfrac43\) · (d) 0

82AASL5-q01055.10 Indefinite integrals and reverse chain rule Paper 1Hard15 marks

Let \(f(x)=2x\,\mathrm{e}^{-x^{2}}\), for \(x\in\mathbb{R}\).

(a)

Show that \(f'(x)=2\left(1-2x^{2}\right)\mathrm{e}^{-x^{2}}\).

(2)
(b)

Find the exact coordinates of the local maximum point on the graph of \(f\).

(3)
(c)

Find \(\displaystyle\int f(x)\,\mathrm{d}x\).

(2)
(d)

Let \(A(k)\) be the area of the region enclosed by the graph of \(f\), the \(x\)-axis and the line \(x=k\), where \(k\gt 0\). Show that \(A(k)=1-\mathrm{e}^{-k^{2}}\).

(2)
(e)

Find the exact value of \(k\) for which \(A(k)=\dfrac12\).

(2)
(f)

Explain why \(A(k)\lt 1\) for all \(k\gt 0\).

(1)
(g)

Hence find the exact value of \(\displaystyle\int_{-1}^{1}|f(x)|\,\mathrm{d}x\).

(3)
Show mark scheme
WorkingMarkNotes
(a)
attempt to use the product rule, with \(\dfrac{\mathrm{d}}{\mathrm{d}x}\mathrm{e}^{-x^{2}}=-2x\,\mathrm{e}^{-x^{2}}\)M1
\(2\mathrm{e}^{-x^{2}}-4x^{2}\mathrm{e}^{-x^{2}}\)A1
\(=2\left(1-2x^{2}\right)\mathrm{e}^{-x^{2}}\)AG
(b)
\(1-2x^{2}=0\)M1Since \(\mathrm{e}^{-x^{2}}\gt 0\).
\(x=\dfrac{1}{\sqrt2}\)A1Must reject \(x=-\tfrac{1}{\sqrt2}\) (a minimum), or justify the maximum, e.g. sign of \(f'\).
\(y=\sqrt2\,\mathrm{e}^{-\frac12}\)A1Accept \(\dfrac{2}{\sqrt2}\mathrm{e}^{-\frac12}\) or \(\sqrt{\dfrac{2}{\mathrm{e}}}\).
(c)
recognizing \(-2x\) as the derivative of \(-x^{2}\), or \(u=-x^{2}\)(M1)
\(-\mathrm{e}^{-x^{2}}+C\)A1
(d)
\(\displaystyle\int_{0}^{k}2x\,\mathrm{e}^{-x^{2}}\,\mathrm{d}x\)M1Must note or use \(f(x)\ge0\) for \(x\ge0\).
\(\left[-\mathrm{e}^{-x^{2}}\right]_{0}^{k}=-\mathrm{e}^{-k^{2}}+1\)A1
\(A(k)=1-\mathrm{e}^{-k^{2}}\)AG
(e)
\(\mathrm{e}^{-k^{2}}=\tfrac12\Rightarrow k^{2}=\ln 2\)(M1)
\(k=\sqrt{\ln 2}\)A1Must reject the negative root.
(f)
\(\mathrm{e}^{-k^{2}}\gt 0\) for all \(k\), so \(1-\mathrm{e}^{-k^{2}}\lt 1\)R1
(g)
\(f(-x)=-f(x)\), so the area from \(-1\) to \(0\) equals the area from \(0\) to \(1\): \(2A(1)\)M1
\(A(1)=1-\mathrm{e}^{-1}\)A1
\(2-2\mathrm{e}^{-1}\)A1Accept \(2-\tfrac{2}{\mathrm{e}}\). Award M0A0A0 for 0 (the signed integral).

Answers: (b) \(\left(\tfrac{1}{\sqrt2},\ \sqrt2\,\mathrm{e}^{-\frac12}\right)\) · (c) \(-\mathrm{e}^{-x^{2}}+C\) · (e) \(k=\sqrt{\ln 2}\) · (g) \(2-2\mathrm{e}^{-1}\)

83AASL5-q01075.11 Definite integrals and areas Paper 1Hard7 marks

The diagram shows the graphs of \(y=\sin2x\) and \(y=\cos x\), for \(0\le x\le\dfrac{\pi}{2}\). The shaded region is enclosed by the two graphs.

xyOπ/6π/2y = sin 2xy = cos x
(a)

Show that the graphs intersect where \(x=\dfrac{\pi}{6}\) and \(x=\dfrac{\pi}{2}\).

(3)
(b)

Find the exact area of the shaded region.

(4)
Show mark scheme
WorkingMarkNotes
(a)
\(2\sin x\cos x=\cos x\)M1Use of the double-angle identity.
\(\cos x(2\sin x-1)=0\)M1Award M0 for dividing by \(\cos x\) without considering \(\cos x=0\).
\(\cos x=0\) or \(\sin x=\tfrac12\)A1
\(x=\dfrac{\pi}{2}\) or \(x=\dfrac{\pi}{6}\)AG
(b)
\(\displaystyle\int_{\pi/6}^{\pi/2}(\sin2x-\cos x)\,\mathrm{d}x\)M1Accept the reverse order of subtraction with an absolute value taken at the end.
\(\left[-\tfrac12\cos2x-\sin x\right]\)A1One mark for both terms correct.
\(\left(-\tfrac12\cos\pi-1\right)-\left(-\tfrac12\cos\tfrac{\pi}{3}-\tfrac12\right)=-\tfrac12-\left(-\tfrac34\right)\)M1Substituting both limits.
\(\dfrac14\)A1

Answers: (b) \(\tfrac14\)

84AASL5-q01115.11 Definite integrals and areas Paper 1Hard10 marks

Let \(f'(x)=\tfrac12x(x-3)(x-5)=\tfrac12\left(x^{3}-8x^{2}+15x\right)\), for \(0\le x\le5\). The diagram shows the graph of \(y=f'(x)\). Region A is enclosed by the graph of \(f'\) and the \(x\)-axis for \(0\le x\le3\), and region B is enclosed by the graph of \(f'\) and the \(x\)-axis for \(3\le x\le5\).

xyO35ABy = f ′(x)

It is given that \(f(0)=2\) and that the area of region B is \(\dfrac{8}{3}\).

(a)

Find the \(x\)-coordinate of the local maximum point on the graph of \(f\). Justify your answer.

(2)
(b)

Show that the area of region A is \(\dfrac{63}{8}\).

(3)
(c)

Find the value of \(f(3)\) and the value of \(f(5)\).

(3)
(d)

Find the least value of \(f(x)\) for \(0\le x\le5\). Justify your answer.

(2)
Show mark scheme
WorkingMarkNotes
(a)
\(x=3\)A1
\(f'\) changes sign from positive to negative at \(x=3\)R1Do not award A1R0.
(b)
\(\displaystyle\int_{0}^{3}\tfrac12\left(x^{3}-8x^{2}+15x\right)\mathrm{d}x\)M1
\(\tfrac12\left[\dfrac{x^{4}}{4}-\dfrac{8x^{3}}{3}+\dfrac{15x^{2}}{2}\right]_{0}^{3}\)A1
\(\tfrac12\left(\dfrac{81}{4}-72+\dfrac{135}{2}\right)=\tfrac12\left(\dfrac{63}{4}\right)\)A1
\(=\dfrac{63}{8}\)AG
(c)
\(f(3)=f(0)+\displaystyle\int_{0}^{3}f'(x)\,\mathrm{d}x\), and \(\displaystyle\int_{3}^{5}f'(x)\,\mathrm{d}x=-\tfrac83\)M1Recognizing that the area of B gives a negative integral.
\(f(3)=2+\dfrac{63}{8}=\dfrac{79}{8}\)A1
\(f(5)=\dfrac{79}{8}-\dfrac{8}{3}=\dfrac{173}{24}\)A1Award A0 for \(\tfrac{301}{24}\) (adding the area of B).
(d)
\(f\) increases on \(0\lt x\lt 3\) and decreases on \(3\lt x\lt 5\), so the least value is at an end point; \(f(5)=\tfrac{173}{24}\gt 2=f(0)\)R1FT from (c).
\(2\)A1Do not award A1R0.

Answers: (a) \(x=3\) · (c) \(f(3)=\tfrac{79}{8},\ f(5)=\tfrac{173}{24}\) · (d) 2

85AASL5-q01135.11 Definite integrals and areas Paper 1Hard9 marks

The line \(y=kx\), where \(k\gt 0\), and the curve \(y=x^{2}\) enclose a region R.

(a)

Find, in terms of \(k\), the \(x\)-coordinates of the points of intersection of the line and the curve.

(2)
(b)

Show that the area of R is \(\dfrac{k^{3}}{6}\).

(3)
(c)

Given that the area of R is 36, find the value of \(k\).

(2)
(d)

For this value of \(k\), show that the line \(x=3\) divides R into two regions of equal area.

(2)
Show mark scheme
WorkingMarkNotes
(a)
\(x^{2}=kx\Rightarrow x(x-k)=0\)(M1)
\(x=0,\ x=k\)A1
(b)
\(\displaystyle\int_{0}^{k}\left(kx-x^{2}\right)\mathrm{d}x\)M1Correct expression with limits.
\(\left[\dfrac{kx^{2}}{2}-\dfrac{x^{3}}{3}\right]_{0}^{k}\)A1
\(\dfrac{k^{3}}{2}-\dfrac{k^{3}}{3}\)A1
\(=\dfrac{k^{3}}{6}\)AG
(c)
\(k^{3}=216\)(M1)
\(k=6\)A1
(d)
\(\displaystyle\int_{0}^{3}\left(6x-x^{2}\right)\mathrm{d}x=\left[3x^{2}-\dfrac{x^{3}}{3}\right]_{0}^{3}\)M1Or a symmetry argument: \(6x-x^{2}=9-(x-3)^{2}\) is symmetric about \(x=3\).
\(27-9=18=\tfrac12(36)\)A1
so \(x=3\) divides R into two regions of equal areaAG

Answers: (a) \(x=0,\ x=k\) · (c) \(k=6\)

86AASL5-q01185.11 Definite integrals and areas Paper 1Hard16 marks

Let \(f(x)=\dfrac{4x}{x^{2}+1}\), for \(x\in\mathbb{R}\). The diagram shows part of the graph of \(f\) and the line L, which is the tangent to the graph of \(f\) at the origin.

xyO1Ly = f(x)
(a)

Show that \(f'(x)=\dfrac{4(1-x^{2})}{(x^{2}+1)^{2}}\).

(3)
(b)

Find the coordinates of the local maximum point and of the local minimum point on the graph of \(f\).

(3)
(c)

The second derivative is \(f''(x)=\dfrac{8x(x^{2}-3)}{(x^{2}+1)^{3}}\). Find the \(x\)-coordinates of the points of inflexion on the graph of \(f\). Justify your answer.

(3)
(d)

Find the equation of L.

(2)
(e)

The shaded region is enclosed by L, the graph of \(f\) and the line \(x=1\). Find the exact area of the shaded region.

(5)
Show mark scheme
WorkingMarkNotes
(a)
attempt to use the quotient ruleM1
\(\dfrac{4(x^{2}+1)-4x(2x)}{(x^{2}+1)^{2}}\)A1
\(\dfrac{4x^{2}+4-8x^{2}}{(x^{2}+1)^{2}}=\dfrac{4-4x^{2}}{(x^{2}+1)^{2}}\)A1
\(f'(x)=\dfrac{4(1-x^{2})}{(x^{2}+1)^{2}}\)AG
(b)
\(1-x^{2}=0\Rightarrow x=\pm1\)M1
local maximum \((1,\,2)\)A1
local minimum \((-1,\,-2)\)A1
(c)
\(8x(x^{2}-3)=0\)M1
\(x=0,\ x=\pm\sqrt3\)A1All three values required.
each is a single root of the numerator and \((x^{2}+1)^{3}\gt 0\), so \(f''\) changes sign at each valueR1Or a sign diagram for \(f''\).
(d)
gradient \(f'(0)=4\)A1
\(y=4x\)A1
(e)
\(\displaystyle\int_{0}^{1}\left(4x-\dfrac{4x}{x^{2}+1}\right)\mathrm{d}x\)M1Award for the difference of their line and \(f\), with limits 0 and 1.
\(\int4x\,\mathrm{d}x=2x^{2}\)A1
recognizing \(2x\) as the derivative of \(x^{2}+1\) (inspection or substitution \(u=x^{2}+1\))M1
\(2\ln(x^{2}+1)\)A1
\(\left[2x^{2}-2\ln(x^{2}+1)\right]_{0}^{1}=2-2\ln2\)A1Accept \(2-\ln4\).

Answers: (b) max \((1,2)\), min \((-1,-2)\) · (c) \(x=0,\ \pm\sqrt3\) · (d) \(y=4x\) · (e) \(2-2\ln2\)

87AASL5-q01195.11 Definite integrals and areas Paper 1Hard16 marks

Let \(f(x)=x\sqrt{9-x^{2}}\), for \(0\le x\le3\). The diagram shows the graph of \(f\) and the line \(y=x\). The graph of \(f\) has a maximum point at M. The line meets the graph of \(f\) at the origin O and at the point P. The shaded region S is enclosed by the graph of \(f\) and the line.

xyO3MPy = xy = f(x)S
(a)

Show that \(f'(x)=\dfrac{9-2x^{2}}{\sqrt{9-x^{2}}}\), for \(0\le x\lt 3\).

(3)
(b)

Find the exact coordinates of M.

(3)
(c)

Find \(\displaystyle\int x\sqrt{9-x^{2}}\,\mathrm{d}x\).

(3)
(d)

Hence find the area of the region enclosed by the graph of \(f\) and the \(x\)-axis.

(2)
(e)

Find the exact \(x\)-coordinate of P.

(2)
(f)

Find the area of S.

(3)
Show mark scheme
WorkingMarkNotes
(a)
attempt to use the product ruleM1
\(\dfrac{\mathrm{d}}{\mathrm{d}x}\sqrt{9-x^{2}}=\dfrac{-x}{\sqrt{9-x^{2}}}\)A1Correct use of the chain rule.
\(\sqrt{9-x^{2}}-\dfrac{x^{2}}{\sqrt{9-x^{2}}}=\dfrac{(9-x^{2})-x^{2}}{\sqrt{9-x^{2}}}\)A1Common denominator must be seen.
\(f'(x)=\dfrac{9-2x^{2}}{\sqrt{9-x^{2}}}\)AG
(b)
\(9-2x^{2}=0\)M1
\(x=\dfrac{3}{\sqrt2}\)A1Accept \(\tfrac{3\sqrt2}{2}\). Must reject the negative root.
\(y=\dfrac{3}{\sqrt2}\sqrt{\dfrac92}=\dfrac92\)A1
(c)
recognizing \(x\) as a multiple of the derivative of \(9-x^{2}\), or \(u=9-x^{2}\), \(\mathrm{d}u=-2x\,\mathrm{d}x\)M1
\(\left(9-x^{2}\right)^{\frac32}\) seen, or \(\displaystyle\int-\tfrac12u^{\frac12}\,\mathrm{d}u\)A1
\(-\dfrac13\left(9-x^{2}\right)^{\frac32}+C\)A1
(d)
\(\left[-\tfrac13\left(9-x^{2}\right)^{\frac32}\right]_{0}^{3}=0-\left(-\tfrac13\times27\right)\)(M1)FT from (c).
\(9\)A1
(e)
\(x\sqrt{9-x^{2}}=x\Rightarrow\sqrt{9-x^{2}}=1\) (for \(x\neq0\))(M1)
\(x=2\sqrt2\)A1Accept \(\sqrt8\).
(f)
\(\displaystyle\int_{0}^{2\sqrt2}\left(x\sqrt{9-x^{2}}-x\right)\mathrm{d}x\)M1Correct expression with limits; FT their (e).
\(\left[-\tfrac13\left(9-x^{2}\right)^{\frac32}-\tfrac12x^{2}\right]_{0}^{2\sqrt2}=\left(-\tfrac13-4\right)-(-9)\)A1
\(\dfrac{14}{3}\)A1

Answers: (b) \(\mathrm{M}\left(\tfrac{3}{\sqrt2},\ \tfrac92\right)\) · (c) \(-\tfrac13(9-x^{2})^{\frac32}+C\) · (d) 9 · (e) \(2\sqrt2\) · (f) \(\tfrac{14}{3}\)

88AASL5-q00055.1 Limits and the derivative Paper 2Easy5 marks

Let \(g(h)=\dfrac{3^{h}-1}{h}\), where \(h\neq0\). The table shows some values of \(g(h)\), correct to four decimal places.

\(h\)\(-0.1\)\(-0.01\)\(-0.001\)\(0.001\)\(0.01\)\(0.1\)
\(g(h)\)1.0404\(p\)1.09801.0992\(q\)1.1612
(a)

Find the value of \(p\) and the value of \(q\).

(2)
(b)

Use the table to write down an estimate, correct to three significant figures, for \(\displaystyle\lim_{h\to0}\dfrac{3^{h}-1}{h}\).

(1)
(c)

The value of \(\dfrac{3^{h}-1}{h}\) is the gradient of the chord joining the points \((0,\,1)\) and \((h,\,3^{h})\) on the curve \(y=3^{x}\). State what the limit in part (b) represents for the curve \(y=3^{x}\).

(1)
(d)

Hence write down the equation of the tangent to \(y=3^{x}\) at the point \((0,\,1)\).

(1)
Show mark scheme
WorkingMarkNotes
(a)
\(p=1.0926\)A1\(1.092599\ldots\)
\(q=1.1047\)A1\(1.104669\ldots\) Award A1A0 for both values correct but not to four decimal places.
(b)
\(1.10\)A1Do not accept \(1.099\) or \(1.1\) (not to three significant figures). The exact value is \(\ln 3=1.0986\ldots\), which is not required.
(c)
the gradient of the tangent to the curve at \((0,\,1)\)A1Accept “the gradient of the curve at \(x=0\)” or “the instantaneous rate of change of \(3^{x}\) at \(x=0\)”.
(d)
\(y=1.10x+1\)A1FT from (b). Accept \(y=1.1x+1\) or \(y=(\ln3)x+1\).

Answers: (a) \(p=1.0926\), \(q=1.1047\) · (b) \(1.10\) · (c) the gradient of the tangent at \((0,1)\) · (d) \(y=1.10x+1\)

89AASL5-q00075.1 Limits and the derivative Paper 2Easy6 marks

A ball is thrown vertically upwards. Its height, \(s\) metres, above the point of release after \(t\) seconds is given by \(s(t)=20t-4.9t^{2}\). The average velocity of the ball between \(t=1\) and \(t=1+h\) is \(\dfrac{s(1+h)-s(1)}{h}\). The table shows some values of this average velocity.

\(h\)\(0.1\)\(0.01\)\(0.001\)
Average velocity (m s−1)9.71\(p\)\(q\)
(a)

Show that the average velocity between \(t=1\) and \(t=1.1\) is \(9.71\) m s−1.

(2)
(b)

Find the value of \(p\) and the value of \(q\).

(2)
(c)

Use the table to estimate the velocity of the ball at the instant \(t=1\).

(1)
(d)

Write down, using derivative notation, the quantity that you have estimated in part (c).

(1)
Show mark scheme
WorkingMarkNotes
(a)
\(s(1.1)=16.071\) and \(s(1)=15.1\)M1Award for both values seen.
\(\dfrac{16.071-15.1}{0.1}=\dfrac{0.971}{0.1}\)A1
\(=9.71\)AG
(b)
\(p=10.151\)A1Accept \(10.2\).
\(q=10.1951\)A1Accept \(10.195\) or \(10.2\).
(c)
\(10.2\) m s−1A1Accept any value in \([10.19,\ 10.2]\).
(d)
\(\dfrac{\mathrm{d}s}{\mathrm{d}t}\) at \(t=1\)A1Accept \(s'(1)\).

Answers: (b) \(p=10.151\), \(q=10.1951\) · (c) \(10.2\) m s−1 · (d) \(s'(1)\)

90AASL5-q00385.5 Introduction to integration Paper 2Easy5 marks

Let \(f(x)=2+3x-x^{2}\). The graph of \(f\) meets the \(x\)-axis at the points where \(x=p\) and \(x=q\), where \(p\lt q\).

(a)

Find the value of \(p\) and the value of \(q\).

(2)
(b)

Write down an integral that represents the area of the region enclosed by the graph of \(f\) and the \(x\)-axis.

(1)
(c)

Find the area of this region.

(1)
(d)

Explain why \(\displaystyle\int_{0}^{5}f(x)\,\mathrm{d}x\) does not give the area of the region enclosed by the graph of \(f\), the \(x\)-axis and the lines \(x=0\) and \(x=5\).

(1)
Show mark scheme
WorkingMarkNotes
(a)
\(p=-0.562\)A1\(-0.561552\ldots\)
\(q=3.56\)A1\(3.56155\ldots\)
(b)
\(\displaystyle\int_{-0.562}^{3.56}(2+3x-x^{2})\,\mathrm{d}x\)A1FT from (a). Accept \(\int_{p}^{q}f(x)\,\mathrm{d}x\) with their values.
(c)
\(11.7\)A1\(11.6821\ldots\) (exactly \(\tfrac{17\sqrt{17}}{6}\))
(d)
\(f(x)\lt 0\) for \(3.56\lt x\le 5\), so part of the region is below the \(x\)-axis and that part contributes a negative value to the integralR1

Answers: (a) \(p=-0.562\), \(q=3.56\) · (c) \(11.7\) · (d) \(f(x)\lt 0\) for part of the interval

91AASL5-q00865.9 Kinematics Paper 2Easy7 marks

A particle moves in a straight line. Its velocity, \(v\ \text{m s}^{-1}\), after \(t\) seconds is given by \(v(t)=\mathrm{e}^{0.5t}-3\), for \(0\le t\le 4\).

(a)

Write down the initial velocity of the particle.

(1)
(b)

Find the value of \(t\) at which the particle changes direction.

(2)
(c)

Find the value of \(t\), for \(t\gt 0\), at which the speed of the particle is again equal to its initial speed.

(2)
(d)

Find the total distance travelled by the particle in the 4 seconds.

(2)
Show mark scheme
WorkingMarkNotes
(a)
\(-2\ \text{m s}^{-1}\)A1
(b)
\(\mathrm{e}^{0.5t}-3=0\), or graph of \(v\) crossing the \(t\)-axis(M1)
\(t=2.20\)A1\(2\ln 3=2.19722\ldots\)
(c)
\(\mathrm{e}^{0.5t}-3=2\)(M1)Recognizing that the velocity must now be \(+2\); \(v=-2\) only at \(t=0\).
\(t=3.22\)A1\(2\ln 5=3.21887\ldots\) Award A0 for \(t=0\).
(d)
\(\displaystyle\int_{0}^{4}\left|\mathrm{e}^{0.5t}-3\right|\mathrm{d}t\)(M1)Or the two separate integrals, split at their (b), added as positive values: \(2.59167\ldots+3.36978\ldots\)
\(5.96\) mA1\(5.96145\ldots\) Award A0 for \(0.778\) (the displacement).

Answers: (a) \(-2\ \text{m s}^{-1}\) · (b) \(t=2.20\) · (c) \(t=3.22\) · (d) 5.96 m

92AASL5-q00065.1 Limits and the derivative Paper 2Medium6 marks

The number of bees, \(N\), in a colony \(t\) weeks after it is established is modelled by \(N(t)=\dfrac{2000}{1+49\mathrm{e}^{-0.6t}}\), for \(t\ge0\).

(a)

Write down the initial number of bees in the colony.

(1)
(b)

Find the rate at which the number of bees is increasing when \(t=4\).

(2)
(c)

Find the value of \(t\) at which the number of bees is increasing most rapidly.

(2)
(d)

Write down the number of bees in the colony at this time.

(1)
Show mark scheme
WorkingMarkNotes
(a)
\(40\)A1
(b)
\(N'(4)\), e.g. GDC derivative at \(t=4\)(M1)
\(180\) bees per weekA1\(179.906\ldots\) Award A0 for \(N(4)=367\).
(c)
maximum of the graph of \(\dfrac{\mathrm{d}N}{\mathrm{d}t}\) on GDC(M1)Or zero of \(N''(t)\).
\(t=6.49\) weeksA1\(6.48636\ldots\ \left(=\dfrac{\ln49}{0.6}\right)\)
(d)
\(1000\)A1

Answers: (a) 40 · (b) 180 bees per week · (c) \(t=6.49\) · (d) 1000

93AASL5-q00085.1 Limits and the derivative Paper 2Medium7 marks

A furniture maker produces \(x\) tables per week. The weekly cost, in euros, of producing \(x\) tables is modelled by \(C(x)=0.001x^{3}-0.3x^{2}+45x+2000\), for \(0\le x\le 250\). The marginal cost is defined as \(C'(x)\).

(a)

Find \(C'(x)\).

(1)
(b)

Find \(C'(150)\) and interpret this value in context.

(2)
(c)

Find the actual increase in the weekly cost when production increases from 150 to 151 tables, and comment on your answer in relation to part (b).

(2)
(d)

Find the values of \(x\) for which the marginal cost is €20 per table.

(2)
Show mark scheme
WorkingMarkNotes
(a)
\(C'(x)=0.003x^{2}-0.6x+45\)A1
(b)
\(C'(150)=22.5\)A1
when 150 tables are made, the cost is increasing at about €22.50 per extra tableR1Must refer to rate of change of cost per table.
(c)
\(C(151)-C(150)=5397.651-5375=\)€\(22.65\)A1\(22.651\) Accept \(22.7\).
this is close to \(C'(150)\), so the marginal cost is a good estimate of the cost of one extra tableR1
(d)
\(0.003x^{2}-0.6x+45=20\), e.g. graph of \(C'\) and \(y=20\)(M1)
\(x=59.2\) or \(x=141\)A1\(59.1751\ldots,\ 140.824\ldots\) Accept \(59\) and \(141\). Award A0 for only one value.

Answers: (a) \(0.003x^{2}-0.6x+45\) · (b) €22.50 per table · (c) €22.65 · (d) \(x=59.2,\ 141\)

94AASL5-q00165.2 Increasing and decreasing functions Paper 2Medium8 marks

The height, \(h\) metres, of a drone above the ground \(t\) seconds after it is switched on is modelled by \(h(t)=0.0004t^{3}-0.036t^{2}+0.8t+5\), for \(0\le t\le 60\).

(a)

Find \(h'(t)\).

(1)
(b)

Find \(h'(10)\) and state what it tells you about the motion of the drone at that time.

(2)
(c)

Find the interval of time during which the drone is descending.

(3)
(d)

Find the height of the drone at the instant it starts to descend.

(2)
Show mark scheme
WorkingMarkNotes
(a)
\(h'(t)=0.0012t^{2}-0.072t+0.8\)A1
(b)
\(0.2\)A1
positive, so the drone is rising (at 0.2 m s−1)R1
(c)
\(h'(t)\lt 0\), e.g. solving \(0.0012t^{2}-0.072t+0.8=0\)M1
\(t=14.7\) and \(t=45.3\)A1\(14.7247\ldots,\ 45.2752\ldots\)
\(14.7\lt t\lt 45.3\)A1Accept non-strict inequalities.
(d)
\(h(14.7247\ldots)\)(M1)
\(10.3\) mA1\(10.2513\ldots\) Accept \(10.25\).

Answers: (a) \(0.0012t^{2}-0.072t+0.8\) · (b) \(0.2\), rising · (c) \(14.7\lt t\lt 45.3\) · (d) \(10.3\) m

95AASL5-q00305.4 Tangents and normals Paper 2Medium6 marks

Let \(f(x)=3\sin x+x\), for \(0\le x\le 2\pi\).

(a)

Find \(f'(x)\).

(1)
(b)

Find the equation of the tangent to the graph of \(f\) at the point where \(x=2\). Give your answer in the form \(y=mx+c\).

(3)
(c)

The tangent meets the graph of \(f\) again at the point Q. Find the \(x\)-coordinate of Q.

(2)
Show mark scheme
WorkingMarkNotes
(a)
\(f'(x)=3\cos x+1\)A1
(b)
\(f(2)=4.72789\ldots\)A1
gradient \(=f'(2)=3\cos2+1=-0.248440\ldots\)(M1)Award for substituting \(x=2\) into their \(f'\) (or using the GDC derivative).
\(y=-0.248x+5.22\)A1\(c=5.22477\ldots\) Accept \(y-4.73=-0.248(x-2)\).
(c)
\(3\sin x+x=-0.248440x+5.22477\), e.g. graph of both or of their difference(M1)
\(x=5.64\)A1\(5.63528\ldots\) Accept \(5.63\) or \(5.64\) (premature rounding of the tangent gives \(5.6347\)). Award A0 for \(x=2\).

Answers: (a) \(f'(x)=3\cos x+1\) · (b) \(y=-0.248x+5.22\) · (c) \(x=5.64\)

96AASL5-q00375.5 Introduction to integration Paper 2Medium5 marks

Let \(f(x)=1+\ln(x^{2}+1)\), for \(x\ge0\). The shaded region R is enclosed by the graph of \(f\), the \(x\)-axis, the \(y\)-axis and the line \(x=3\).

xyO3Ry = f(x)
(a)

Write down an integral that represents the area of R.

(1)
(b)

Find the area of R.

(1)
(c)

The line \(x=k\) divides R into two regions of equal area. Find the value of \(k\).

(3)
Show mark scheme
WorkingMarkNotes
(a)
\(\displaystyle\int_{0}^{3}\big(1+\ln(x^{2}+1)\big)\,\mathrm{d}x\)A1Accept the absence of d\(x\).
(b)
\(6.41\)A1\(6.40584\ldots\)
(c)
\(\displaystyle\int_{0}^{k}\big(1+\ln(x^{2}+1)\big)\,\mathrm{d}x=\tfrac12\times6.40584\ldots\)(M1)Or \(\int_{0}^{k}f=\int_{k}^{3}f\).
\(=3.20292\ldots\)(A1)
\(k=1.91\)A1\(1.91052\ldots\) Award A1 only for a value with \(0\lt k\lt 3\).

Answers: (b) \(6.41\) · (c) \(k=1.91\)

97AASL5-q00395.5 Introduction to integration Paper 2Medium7 marks

Let \(f(x)=kx(4-x)^{2}\), where \(k\gt 0\). The following diagram shows part of the graph of \(f\). The shaded region R is enclosed by the graph of \(f\) and the \(x\)-axis, for \(0\le x\le 4\).

xyO4Ry = kx(4 − x)²
Diagram not to scale
(a)

Write down an integral, in terms of \(k\), that represents the area of R.

(1)
(b)

The area of R is 32 square units. Find the value of \(k\).

(3)
(c)

By expanding \(f(x)\), find the equation of the tangent to the graph of \(f\) at the origin.

(3)
Show mark scheme
WorkingMarkNotes
(a)
\(\displaystyle\int_{0}^{4}kx(4-x)^{2}\,\mathrm{d}x\)A1
(b)
\(k\displaystyle\int_{0}^{4}x(4-x)^{2}\,\mathrm{d}x=32\)(M1)
\(\displaystyle\int_{0}^{4}x(4-x)^{2}\,\mathrm{d}x=21.3\)(A1)\(21.333\ldots=\tfrac{64}{3}\)
\(k=1.5\)A1
(c)
\(f(x)=k(16x-8x^{2}+x^{3})\), so \(f'(x)=k(16-16x+3x^{2})\)(M1)
\(f'(0)=16k=24\)(A1)FT from their \(k\).
\(y=24x\)A1

Answers: (a) \(\int_0^4 kx(4-x)^2\,\mathrm{d}x\) · (b) \(k=1.5\) · (c) \(y=24x\)

98AASL5-q00405.5 Introduction to integration Paper 2Medium14 marks

During a storm, the rate of rainfall, \(r\) millimetres per hour, \(t\) hours after the storm begins is modelled by \(r(t)=0.1t^{2}(9-t)\), for \(0\le t\le 9\).

(a)

Find the rate of rainfall when \(t=5\).

(1)
(b)

Find \(r'(t)\).

(2)
(c)

Find the interval of time during which the rate of rainfall is increasing.

(3)
(d)

Find \(r'(7)\) and interpret your answer in context.

(2)
(e)

Find the total rainfall during the storm.

(2)
(f)

Find the rainfall during the last three hours of the storm.

(2)
(g)

Find the time at which half of the total rainfall has fallen.

(2)
Show mark scheme
WorkingMarkNotes
(a)
\(10\) mm per hourA1
(b)
\(r(t)=0.9t^{2}-0.1t^{3}\) or \(1.8t\)A1Award for expanding correctly or for one correct term of \(r'(t)\).
\(r'(t)=1.8t-0.3t^{2}\)A1
(c)
\(1.8t-0.3t^{2}=0\) or \(r'(t)\gt 0\)M1
\(0.3t(6-t)=0\Rightarrow t=0,\ t=6\)A1
\(0\lt t\lt 6\)A1Accept \(0\le t\le 6\).
(d)
\(r'(7)=-2.1\)A1
the rate of rainfall is decreasing at 2.1 mm per hour, per hourR1Must refer to the rate of rainfall decreasing; units not required.
(e)
\(\displaystyle\int_{0}^{9}0.1t^{2}(9-t)\,\mathrm{d}t\)(M1)
\(54.7\) mmA1\(54.675\) (exactly \(\tfrac{2187}{40}\))
(f)
\(\displaystyle\int_{6}^{9}r(t)\,\mathrm{d}t\)(M1)
\(22.3\) mmA1\(22.275\)
(g)
\(\displaystyle\int_{0}^{T}r(t)\,\mathrm{d}t=27.3375\)(M1)FT from (e).
\(T=5.53\) hoursA1\(5.52845\ldots\)

Answers: (a) 10 mm h−1 · (b) \(1.8t-0.3t^{2}\) · (c) \(0\lt t\lt 6\) · (d) \(-2.1\) · (e) 54.7 mm · (f) 22.3 mm · (g) \(5.53\) h

99AASL5-q00535.6 Differentiation rules Paper 2Medium7 marks

The height, \(h\) metres, of a seat on a Ferris wheel above the ground \(t\) minutes after it passes the lowest point is modelled by \(h(t)=36-32\cos\left(\dfrac{\pi t}{15}\right)\), for \(0\le t\le30\).

(a)

Find \(h'(t)\).

(2)
(b)

Find the rate at which the height of the seat is changing when \(t=4\).

(1)
(c)

Find the maximum rate at which the height of the seat increases, and the value of \(t\) at which it occurs.

(2)
(d)

Find the values of \(t\) for which the height of the seat is increasing at a rate of 5 metres per minute.

(2)
Show mark scheme
WorkingMarkNotes
(a)
attempt to use the chain rule, e.g. \(\sin\left(\tfrac{\pi t}{15}\right)\times\tfrac{\pi}{15}\)M1
\(h'(t)=\dfrac{32\pi}{15}\sin\left(\dfrac{\pi t}{15}\right)\)A1
(b)
\(4.98\) m min−1A1\(4.98060\ldots\)
(c)
\(6.70\) m min−1A1\(6.70206\ldots\ \left(=\tfrac{32\pi}{15}\right)\)
\(t=7.5\)A1
(d)
\(\dfrac{32\pi}{15}\sin\left(\dfrac{\pi t}{15}\right)=5\), e.g. intersection on GDC(M1)
\(t=4.02\) and \(t=11.0\)A1\(4.02070\ldots\), \(10.9793\ldots\) Both values required.

Answers: (a) \(\dfrac{32\pi}{15}\sin\left(\dfrac{\pi t}{15}\right)\) · (b) 4.98 m min−1 · (c) 6.70 m min−1 at \(t=7.5\) · (d) \(t=4.02,\ 11.0\)

100AASL5-q00545.6 Differentiation rules Paper 2Medium9 marks

Let \(f(x)=4\ln x\) and \(g(x)=\mathrm{e}^{\frac{x}{2}}\), for \(x\gt 0\). The graphs of \(f\) and \(g\) intersect at \(x=a\) and \(x=b\), where \(a\lt b\).

(a)

Find \(f'(x)\) and \(g'(x)\).

(2)
(b)

Find the value of \(x\) at which the tangents to the two graphs are parallel.

(2)
(c)

Find the value of \(a\) and the value of \(b\).

(2)
(d)

For \(a\le x\le b\), let \(d(x)=f(x)-g(x)\). Explain why \(d\) has its maximum value at your answer to part (b), and find this maximum value.

(3)
Show mark scheme
WorkingMarkNotes
(a)
\(f'(x)=\dfrac{4}{x}\)A1
\(g'(x)=\dfrac12\mathrm{e}^{\frac{x}{2}}\)A1
(b)
\(\dfrac{4}{x}=\dfrac12\mathrm{e}^{\frac{x}{2}}\), e.g. intersection on GDC(M1)
\(x=2.40\)A1\(2.40433\ldots\)
(c)
\(a=1.92\)A1\(1.92306\ldots\)
\(b=2.89\)A1\(2.89429\ldots\)
(d)
\(d'(x)=f'(x)-g'(x)=0\) where the tangents are parallelR1Accept: this is the only stationary point of \(d\), and \(d(a)=d(b)=0\) with \(d\gt 0\) between.
\(d(2.40433\ldots)=4\ln(2.40433\ldots)-\mathrm{e}^{1.20216\ldots}\)(M1)
\(0.182\)A1\(0.181772\ldots\) Accept 0.181 or 0.182.

Answers: (b) \(x=2.40\) · (c) \(a=1.92,\ b=2.89\) · (d) \(0.182\)

101AASL5-q00655.7 The second derivative and graphs Paper 2Medium7 marks

Let \(g(x)=\mathrm{e}^{-\frac{x}{2}}\sin(2x)\), for \(0\le x\le\pi\).

(a)

Find the coordinates of the local maximum point on the graph of \(g\).

(2)
(b)

Find the \(x\)-coordinates of the points of inflexion on the graph of \(g\).

(2)
(c)

Write down the interval on which the graph of \(g\) is concave-up.

(1)
(d)

Find the least value of \(g'(x)\) for \(0\le x\le\pi\).

(2)
Show mark scheme
WorkingMarkNotes
(a)
\(x=0.663\)A1\(0.662908\ldots\)
\(y=0.696\)A1\(0.696444\ldots\)
(b)
\(x=1.33\)A1\(1.32581\ldots\) Use of GDC on the graph of \(g'\) (turning points) or of \(g''\) (zeros).
\(x=2.90\)A1\(2.89661\ldots\)
(c)
\(1.33\lt x\lt 2.90\)A1FT from their (b).
(d)
minimum of the graph of \(y=g'(x)\) on GDC, at \(x=1.33\)(M1)Endpoint values \(g'(0)=2\) and \(g'(\pi)=0.416\) are greater.
\(-1.03\)A1\(-1.03070\ldots\)

Answers: (a) \((0.663,\ 0.696)\) · (b) \(x=1.33,\ 2.90\) · (c) \(1.33\lt x\lt2.90\) · (d) \(-1.03\)

102AASL5-q00755.8 Stationary points, inflexion and optimization Paper 2Medium8 marks

The diagram shows part of the graph of \(y=6\cos\left(\dfrac{x}{2}\right)\), for \(-\pi\le x\le\pi\). The rectangle ABCD has vertices \(\text{A}(-x,\,0)\) and \(\text{B}(x,\,0)\) on the \(x\)-axis, where \(0\lt x\lt\pi\), and vertices C and D on the curve.

xyO−ππABCDy = 6 cos(x/2)
(a)

Show that the area of the rectangle is \(A=12x\cos\left(\dfrac{x}{2}\right)\).

(2)
(b)

Find the maximum area of the rectangle.

(3)
(c)

Find the maximum perimeter of the rectangle.

(3)
Show mark scheme
WorkingMarkNotes
(a)
width \(\text{AB}=2x\)A1
height \(\text{BC}=6\cos\left(\tfrac{x}{2}\right)\), so \(A=2x\times6\cos\left(\tfrac{x}{2}\right)\)A1
\(A=12x\cos\left(\tfrac{x}{2}\right)\)AG
(b)
use of GDC to find the maximum of \(A\), e.g. graph, or solving \(\dfrac{\mathrm{d}A}{\mathrm{d}x}=0\)(M1)
\(x=1.72066\ldots\)(A1)
maximum area \(=13.5\)A1\(13.4663\ldots\)
(c)
perimeter \(P=4x+12\cos\left(\tfrac{x}{2}\right)\)A1
use of GDC to find the maximum of \(P\) (at \(x=1.45946\ldots\))(M1)Or \(\dfrac{\mathrm{d}P}{\mathrm{d}x}=4-6\sin\left(\tfrac{x}{2}\right)=0\).
maximum perimeter \(=14.8\)A1\(14.7821\ldots\)

Answers: (b) \(13.5\) · (c) \(14.8\)

103AASL5-q00775.8 Stationary points, inflexion and optimization Paper 2Medium8 marks

A small factory makes \(x\) bicycles per month, where \(0\le x\le100\). The monthly profit, in dollars, is modelled by \(P(x)=-0.01x^{3}+0.6x^{2}+30x-400\).

(a)

Find \(P'(x)\).

(1)
(b)

Find the value of \(x\) for which \(P'(x)=0\).

(2)
(c)

Use the second derivative to show that this value of \(x\) gives a maximum.

(2)
(d)

The factory can only make a whole number of bicycles. Find the number of bicycles that maximizes the monthly profit, and the maximum monthly profit.

(3)
Show mark scheme
WorkingMarkNotes
(a)
\(P'(x)=-0.03x^{2}+1.2x+30\)A1
(b)
\(-0.03x^{2}+1.2x+30=0\), e.g. GDC(M1)Equivalent to \(x^{2}-40x-1000=0\).
\(x=57.4\)A1\(57.4165\ldots\ \left(=20+\sqrt{1400}\right)\); reject the negative root.
(c)
\(P''(x)=-0.06x+1.2\)A1
\(P''(57.4)=-2.24\lt 0\), so a maximumR1\(-2.24499\ldots\)
(d)
comparing \(P(57)\) and \(P(58)\)(M1)\(P(57)=1407.47\), \(P(58)=1407.28\); endpoints \(P(0)=-400\), \(P(100)=-1400\).
57 bicyclesA1
$1407.47A1Award A0 for \(P(57.4)=1407.66\).

Answers: (a) \(-0.03x^{2}+1.2x+30\) · (b) \(x=57.4\) · (d) 57 bicycles, $1407.47

104AASL5-q00785.8 Stationary points, inflexion and optimization Paper 2Medium9 marks

A lorry travels 600 km at a constant speed of \(v\) km h−1. The driver is paid $24 per hour. The cost of fuel is \(0.00006v^{2}\) dollars per kilometre. Let \(C\) be the total cost, in dollars, of the journey.

(a)

Show that \(C(v)=\dfrac{14\,400}{v}+0.036v^{2}\).

(2)
(b)

Find the speed for which the total cost is a minimum.

(3)
(c)

Justify that this speed gives a minimum.

(1)
(d)

Find the minimum total cost.

(1)
(e)

Regulations require the lorry to travel at a speed between 70 km h−1 and 90 km h−1. Find the minimum total cost under these regulations. Justify your answer.

(2)
Show mark scheme
WorkingMarkNotes
(a)
time \(=\dfrac{600}{v}\) hours, so driver’s pay \(=24\times\dfrac{600}{v}=\dfrac{14\,400}{v}\)A1
fuel \(=600\times0.00006v^{2}=0.036v^{2}\)A1
\(C(v)=\dfrac{14\,400}{v}+0.036v^{2}\)AG
(b)
\(C'(v)=-\dfrac{14\,400}{v^{2}}+0.072v=0\)M1Or minimum of \(C\) on GDC.
\(v^{3}=200\,000\)A1
\(v=58.5\) km h−1A1\(58.4803\ldots\)
(c)
\(C''(v)=\dfrac{28\,800}{v^{3}}+0.072\gt 0\) for \(v\gt 0\)R1Or \(C'\) changes from negative to positive.
(d)
$369.35A1\(369.354\ldots\) Accept $369.
(e)
\(C'(v)\gt 0\) for \(v\gt 58.5\), so \(C\) is increasing on \(70\le v\le90\) and the minimum is at \(v=70\)R1
$382.11A1\(382.114\ldots\) Accept $382.

Answers: (b) 58.5 km h−1 · (d) $369.35 · (e) $382.11 at 70 km h−1

105AASL5-q00895.9 Kinematics Paper 2Medium8 marks

A particle starts from a fixed point O and moves in a straight line. Its velocity, \(v\ \text{m s}^{-1}\), after \(t\) seconds is given by \(v(t)=1-3\sin(1.2t)\), for \(0\le t\le5\).

(a)

Find the first time at which the particle is at rest.

(2)
(b)

Find the number of times the particle changes direction during the 5 seconds. Justify your answer.

(2)
(c)

Find the total distance travelled by the particle.

(2)
(d)

Find the distance of the particle from O when \(t=5\).

(2)
Show mark scheme
WorkingMarkNotes
(a)
\(1-3\sin(1.2t)=0\), or first zero of \(v\) on the GDC(M1)
\(t=0.283\) sA1\(0.283197\ldots\)
(b)
\(v\) changes sign at \(t=0.283\) and at \(t=2.33\) only; the next zero, \(t=5.52\), is outside the intervalR1\(2.33479\ldots\) and \(5.51918\ldots\) Accept a sketch of \(v\) showing exactly two sign changes.
2 timesA1Do not award A1R0.
(c)
\(\displaystyle\int_{0}^{5}|1-3\sin(1.2t)|\,\mathrm{d}t\)(M1)
\(10.2\) mA1\(10.2253\ldots\)
(d)
\(\left|\displaystyle\int_{0}^{5}(1-3\sin(1.2t))\,\mathrm{d}t\right|\)(M1)
\(4.90\) mA1\(4.90042\ldots\) Award A0 for \(10.2\).

Answers: (a) \(t=0.283\) s · (b) 2 · (c) 10.2 m · (d) 4.90 m

106AASL5-q00905.9 Kinematics Paper 2Medium8 marks

A sprinter starts from rest at the start line of a 100 m race. Her velocity, \(v\ \text{m s}^{-1}\), \(t\) seconds after the start is modelled by \(v(t)=11\left(1-\mathrm{e}^{-0.8t}\right)\), for \(t\ge0\).

(a)

Find her initial acceleration.

(2)
(b)

Write down the velocity that the model predicts she approaches.

(1)
(c)

Find the distance she runs in the first 5 seconds.

(2)
(d)

Find the time she takes to complete the 100 m race.

(3)
Show mark scheme
WorkingMarkNotes
(a)
\(a(t)=8.8\,\mathrm{e}^{-0.8t}\), or GDC derivative at \(t=0\)(M1)
\(8.8\ \text{m s}^{-2}\)A1
(b)
\(11\ \text{m s}^{-1}\)A1
(c)
\(\displaystyle\int_{0}^{5}11\left(1-\mathrm{e}^{-0.8t}\right)\mathrm{d}t\)(M1)
\(41.5\) mA1\(41.5018\ldots\)
(d)
\(\displaystyle\int_{0}^{T}11\left(1-\mathrm{e}^{-0.8t}\right)\mathrm{d}t=100\)M1
\(11T-13.75\left(1-\mathrm{e}^{-0.8T}\right)=100\), or graph/table of the integral(A1)Award for any correct method of solving their equation with technology.
\(T=10.3\) sA1\(10.3405\ldots\)

Answers: (a) \(8.8\ \text{m s}^{-2}\) · (b) \(11\ \text{m s}^{-1}\) · (c) 41.5 m · (d) 10.3 s

107AASL5-q01145.11 Definite integrals and areas Paper 2Medium7 marks

Let \(f(x)=6-0.5x^{2}\) and \(g(x)=\mathrm{e}^{0.5x}\). The shaded region R is enclosed by the graphs of \(f\) and \(g\).

xyOy = f(x)y = g(x)R
(a)

Find the \(x\)-coordinates of the points of intersection of the two graphs.

(2)
(b)

Find the area of R.

(2)
(c)

Find the maximum vertical distance between the graphs of \(f\) and \(g\) within R.

(3)
Show mark scheme
WorkingMarkNotes
(a)
\(6-0.5x^{2}=\mathrm{e}^{0.5x}\), e.g. intersections on GDC(M1)
\(x=-3.41\) and \(x=2.35\)A1\(-3.41125\ldots\), \(2.35015\ldots\)
(b)
\(\displaystyle\int_{-3.41125}^{2.35015}\big(6-0.5x^{2}-\mathrm{e}^{0.5x}\big)\,\mathrm{d}x\)(M1)FT their limits from (a).
\(19.7\)A1\(19.6756\ldots\)
(c)
\(d(x)=6-0.5x^{2}-\mathrm{e}^{0.5x}\)(M1)
maximum of \(d\) on GDC, or \(d'(x)=-x-0.5\mathrm{e}^{0.5x}=0\Rightarrow x=-0.408\)(M1)\(-0.407776\ldots\)
\(5.10\)A1\(5.10130\ldots\)

Answers: (a) \(x=-3.41,\ 2.35\) · (b) \(19.7\) · (c) \(5.10\)

108AASL5-q01155.11 Definite integrals and areas Paper 2Medium7 marks

Let \(f(x)=3\ln(x+1)\) and \(g(x)=x^{2}-2x\), for \(x\ge0\). The graphs of \(f\) and \(g\) meet at the origin and at a second point. The shaded region R is enclosed by the two graphs.

xyOy = f(x)y = g(x)R
(a)

Find the \(x\)-coordinate of the second point of intersection.

(2)
(b)

Write down an integral that represents the area of R.

(1)
(c)

Find the area of R.

(1)
(d)

The line \(x=a\) divides R into two regions of equal area. Find the value of \(a\).

(3)
Show mark scheme
WorkingMarkNotes
(a)
\(3\ln(x+1)=x^{2}-2x\), or intersection on the GDC(M1)
\(x=3.32\)A1\(3.32186\ldots\)
(b)
\(\displaystyle\int_{0}^{3.32186\ldots}\left(3\ln(x+1)-x^{2}+2x\right)\mathrm{d}x\)A1FT from (a). Must include correct limits and the difference in the correct order (or with a modulus).
(c)
\(7.83\)A1\(7.82807\ldots\)
(d)
\(\displaystyle\int_{0}^{a}\big(f(x)-g(x)\big)\,\mathrm{d}x=\tfrac12(7.82807\ldots)\)M1Or equating the two parts of R.
\(\displaystyle\int_{0}^{a}\big(f(x)-g(x)\big)\,\mathrm{d}x=3.91403\ldots\)(A1)
\(a=1.62\)A1\(1.61893\ldots\)

Answers: (a) \(x=3.32\) · (c) 7.83 · (d) \(a=1.62\)

109AASL5-q01165.11 Definite integrals and areas Paper 2Medium6 marks

Let \(h(x)=\sqrt{1+x^{3}}\), for \(x\ge0\).

(a)

Find \(\displaystyle\int_{0}^{2}h(x)\,\mathrm{d}x\).

(2)
(b)

Given that \(\displaystyle\int_{0}^{k}h(x)\,\mathrm{d}x=5\), where \(k\gt 0\), find the value of \(k\).

(3)
(c)

Explain why there is only one value of \(k\gt 0\) that satisfies the equation in part (b).

(1)
Show mark scheme
WorkingMarkNotes
(a)
use of GDC integration with the correct function and limits(M1)
\(3.24\)A1\(3.24130\ldots\)
(b)
\(\displaystyle\int_{0}^{k}\sqrt{1+x^{3}}\,\mathrm{d}x-5=0\), or a graph of \(y=\displaystyle\int_{0}^{x}h(t)\,\mathrm{d}t\) and \(y=5\)M1
\(k\gt 2\) since \(3.24\lt 5\)(A1)Or a sensible table of values of the integral.
\(k=2.50\)A1\(2.49891\ldots\)
(c)
\(h(x)\gt 0\), so \(\displaystyle\int_{0}^{k}h(x)\,\mathrm{d}x\) increases as \(k\) increases; it can equal 5 only onceR1

Answers: (a) 3.24 · (b) \(k=2.50\)

110AASL5-q01175.11 Definite integrals and areas Paper 2Medium7 marks

Let \(f(x)=x\cos x\), for \(0\le x\le4\).

(a)

Find the value of \(x\), for \(0\lt x\lt 4\), at which the graph of \(f\) meets the \(x\)-axis.

(1)
(b)

Find \(\displaystyle\int_{0}^{4}f(x)\,\mathrm{d}x\).

(2)
(c)

Find the total area of the region enclosed by the graph of \(f\), the \(x\)-axis and the line \(x=4\).

(2)
(d)

Find the value of \(b\), where \(0\lt b\lt 4\), for which \(\displaystyle\int_{0}^{b}f(x)\,\mathrm{d}x=0\).

(2)
Show mark scheme
WorkingMarkNotes
(a)
\(x=1.57\)A1\(\tfrac{\pi}{2}=1.57079\ldots\)
(b)
use of GDC integration with correct limits(M1)
\(-4.68\)A1\(-4.68085\ldots\)
(c)
\(\displaystyle\int_{0}^{4}|x\cos x|\,\mathrm{d}x\), or \(0.570796\ldots+|-5.25164\ldots|\)(M1)
\(5.82\)A1\(5.82244\ldots\)
(d)
\(\displaystyle\int_{0}^{b}x\cos x\,\mathrm{d}x=0\), e.g. graph of \(y=\displaystyle\int_{0}^{x}f(u)\,\mathrm{d}u\) and its zero, or equating the area below the axis from \(1.57\) to \(b\) with \(0.571\)(M1)
\(b=2.33\)A1\(2.33112\ldots\) Award A0 for \(b=1.57\).

Answers: (a) \(x=1.57\) · (b) \(-4.68\) · (c) 5.82 · (d) \(b=2.33\)

111AASL5-q00175.2 Increasing and decreasing functions Paper 2Hard16 marks

The cross-section of a garden mound is modelled by \(d(x)=\dfrac{-x^{3}+8x^{2}+48x}{80}\), for \(0\le x\le 12\), where \(d\) is the height of the mound in metres at a horizontal distance \(x\) metres from one end.

(a)

Find \(d'(x)\).

(2)
(b)

Find the gradient of the mound at \(x=4\), and state whether the mound is rising or falling there.

(2)
(c)

Find the set of values of \(x\) for which the height of the mound is increasing.

(3)
(d)

Write down the maximum height of the mound.

(1)
(e)(i)

A straight wooden beam rests along the tangent to the mound at the point where \(x=10\).

Find the equation of this tangent.

(3)
(e)(ii)

Find the value of \(x\) at which the beam reaches the ground.

(1)
(f)

Find the area of the cross-section of the mound.

(2)
(g)

Find the horizontal width of the part of the mound that is more than 2 m high.

(2)
Show mark scheme
WorkingMarkNotes
(a)
\(\dfrac{-3x^{2}+16x}{80}\)A1Award for any two correct terms.
\(d'(x)=\dfrac{-3x^{2}+16x+48}{80}\)A1Accept \(-0.0375x^{2}+0.2x+0.6\).
(b)
\(d'(4)=0.8\)A1
positive, so risingR1
(c)
\(d'(x)\gt 0\), e.g. solving \(-3x^{2}+16x+48=0\)M1
\(x=7.47\)A1\(7.47406\ldots\) (the other root, \(-2.14\), is outside the domain)
\(0\le x\lt 7.47\)A1Accept \(0\lt x\lt 7.47\).
(d)
\(4.85\) mA1\(4.85168\ldots\)
(e)(i)
\(d(10)=3.5\)(A1)
\(d'(10)=-1.15\)(A1)
\(y=-1.15x+15\)A1Accept \(y-3.5=-1.15(x-10)\).
(e)(ii)
\(x=13.0\)A1\(13.0434\ldots\) FT from (e)(i).
(f)
\(\displaystyle\int_{0}^{12}d(x)\,\mathrm{d}x\)(M1)
\(36\ \text{m}^{2}\)A1
(g)
\(d(x)=2\Rightarrow x=2.58\) or \(x=11.0\)(M1)\(2.58118\ldots,\ 11.0357\ldots\)
\(8.45\) mA1\(8.45455\ldots\)

Answers: (a) \(\frac{-3x^{2}+16x+48}{80}\) · (b) \(0.8\), rising · (c) \(0\le x\lt 7.47\) · (d) \(4.85\) m · (e)(i) \(y=-1.15x+15\) (ii) \(x=13.0\) · (f) \(36\) m2 · (g) \(8.45\) m

112AASL5-q00315.4 Tangents and normals Paper 2Hard8 marks

Let \(f(x)=\dfrac{12}{1+x^{2}}\), for \(-5\le x\le 5\).

(a)

Use your graphic display calculator to find the gradient of the graph of \(f\) at the point where \(x=1\).

(1)
(b)

Find the equation of the normal to the graph of \(f\) at the point where \(x=1\).

(3)
(c)

The normal meets the graph of \(f\) again at the point A. Find the \(x\)-coordinate of A.

(2)
(d)

There is one other point on the graph of \(f\) at which the tangent is parallel to the tangent at \(x=1\). Find the \(x\)-coordinate of this point.

(2)
Show mark scheme
WorkingMarkNotes
(a)
\(-6\)A1
(b)
\(f(1)=6\)(A1)
gradient of normal \(=\dfrac{1}{6}\)(M1)
\(y-6=\dfrac{1}{6}(x-1)\)A1Accept \(y=\dfrac{1}{6}x+\dfrac{35}{6}\) or \(y=0.167x+5.83\).
(c)
\(\dfrac{12}{1+x^{2}}=\dfrac{1}{6}x+\dfrac{35}{6}\), e.g. intersection of graphs(M1)
\(x=-1.06\)A1\(-1.05888\ldots\)
(d)
graph of \(y=f'(x)\) and \(y=-6\), or solving \(f'(x)=-6\)(M1)
\(x=0.296\)A1\(0.295597\ldots\) Award A0 for \(x=1\).

Answers: (a) \(-6\) · (b) \(y=\frac16x+\frac{35}{6}\) · (c) \(-1.06\) · (d) \(0.296\)

113AASL5-q00665.7 The second derivative and graphs Paper 2Hard13 marks

The concentration of a drug in a patient’s blood, \(C\) milligrams per litre (mg L−1), \(t\) hours after a tablet is taken is modelled by \(C(t)=12\left(\mathrm{e}^{-0.2t}-\mathrm{e}^{-0.8t}\right)\), for \(t\ge0\).

(a)

Write down the value of \(C(0)\).

(1)
(b)

Find \(C'(t)\).

(2)
(c)

Show that the concentration is a maximum when \(t=\dfrac{5}{3}\ln4\).

(3)
(d)

Find the maximum concentration.

(1)
(e)

Find the time at which the concentration is decreasing most rapidly, and the rate of decrease at this time.

(3)
(f)

The drug is effective while the concentration is at least 3 mg L−1. Find the length of time for which the drug is effective.

(3)
Show mark scheme
WorkingMarkNotes
(a)
\(0\)A1
(b)
\(-2.4\mathrm{e}^{-0.2t}\)A1
\(+9.6\mathrm{e}^{-0.8t}\)A1\(C'(t)=-2.4\mathrm{e}^{-0.2t}+9.6\mathrm{e}^{-0.8t}\)
(c)
\(C'(t)=0\Rightarrow9.6\mathrm{e}^{-0.8t}=2.4\mathrm{e}^{-0.2t}\)M1
\(\mathrm{e}^{0.6t}=4\)A1
\(t=\dfrac{\ln4}{0.6}\), and \(C'\) changes from positive to negative (or \(C''\lt 0\) there)A1\(C''\left(\tfrac53\ln4\right)=-0.907\ldots\lt 0\).
\(t=\dfrac{5}{3}\ln4\)AG
(d)
\(5.67\) mg L−1A1\(5.66964\ldots\ \left(=9\times4^{-\frac13}\right)\)
(e)
\(C''(t)=0\), or minimum of the graph of \(C'\) on GDC(M1)
\(t=4.62\) hoursA1\(4.62098\ldots\ \left(=\tfrac53\ln16\right)\)
decreasing at \(0.714\) mg L−1 h−1A1\(C'(4.62\ldots)=-0.714330\ldots\) Accept \(-0.714\).
(f)
\(C(t)=3\), e.g. intersection on GDC(M1)
\(t=0.545\) and \(t=6.85\)A1\(0.544666\ldots\), \(6.84868\ldots\)
\(6.30\) hoursA1\(6.30402\ldots\) Accept 6.30–6.31 (6.305 from rounded values).

Answers: (a) 0 · (b) \(-2.4\mathrm{e}^{-0.2t}+9.6\mathrm{e}^{-0.8t}\) · (d) 5.67 mg L−1 · (e) \(t=4.62\) h, 0.714 mg L−1 h−1 · (f) 6.30 h

114AASL5-q00765.8 Stationary points, inflexion and optimization Paper 2Hard9 marks

A closed cylindrical container of radius \(r\) cm and height \(h\) cm has a volume of \(500\ \text{cm}^{3}\). The material for the curved surface and the top costs 2 cents per cm2. The material for the base costs 4 cents per cm2. Let \(C\) be the total cost of the material, in cents.

(a)

Write down an expression for \(h\) in terms of \(r\).

(1)
(b)

Show that \(C=6\pi r^{2}+\dfrac{2000}{r}\).

(2)
(c)

Find \(\dfrac{\mathrm{d}C}{\mathrm{d}r}\).

(2)
(d)

Find the value of \(r\) for which the cost is a minimum. Justify that this value gives a minimum.

(3)
(e)

Find the minimum cost, in dollars, correct to the nearest cent.

(1)
Show mark scheme
WorkingMarkNotes
(a)
\(h=\dfrac{500}{\pi r^{2}}\)A1
(b)
\(C=2(2\pi rh)+2(\pi r^{2})+4(\pi r^{2})\)M1Award for a cost expression with the three surfaces and correct prices.
\(4\pi r\times\dfrac{500}{\pi r^{2}}+6\pi r^{2}\)A1Substitution of their \(h\).
\(C=6\pi r^{2}+\dfrac{2000}{r}\)AG
(c)
\(12\pi r\)A1
\(-2000r^{-2}\)A1\(\dfrac{\mathrm{d}C}{\mathrm{d}r}=12\pi r-\dfrac{2000}{r^{2}}\)
(d)
\(12\pi r-\dfrac{2000}{r^{2}}=0\Rightarrow r^{3}=\dfrac{500}{3\pi}\)M1Or use of GDC on their derivative or on \(C\).
\(r=3.76\)A1\(3.75750\ldots\)
\(\dfrac{\mathrm{d}^{2}C}{\mathrm{d}r^{2}}=12\pi+\dfrac{4000}{r^{3}}\gt 0\) for \(r\gt 0\), so a minimumR1Accept a sign change of \(\dfrac{\mathrm{d}C}{\mathrm{d}r}\) from negative to positive, with values shown.
(e)
$7.98A1\(798.402\ldots\) cents. Award A0 for 798 or 7.984.

Answers: (a) \(h=\dfrac{500}{\pi r^{2}}\) · (c) \(12\pi r-\dfrac{2000}{r^{2}}\) · (d) \(r=3.76\) · (e) $7.98

115AASL5-q00795.8 Stationary points, inflexion and optimization Paper 2Hard13 marks

An open gutter is made by bending a sheet of metal 50 cm wide. The cross-section is a trapezium with a horizontal base of 20 cm and two sloping sides of 15 cm, each making an angle \(\theta\) with the horizontal, where \(0\lt\theta\le\dfrac{\pi}{2}\), as shown in the diagram.

θ20 cm15 cm15 cm
Diagram not to scale
(a)

Show that the area of the cross-section, \(A\ \text{cm}^{2}\), is given by \(A=300\sin\theta+225\sin\theta\cos\theta\).

(3)
(b)

Find \(\dfrac{\mathrm{d}A}{\mathrm{d}\theta}\).

(3)
(c)

Show that \(\dfrac{\mathrm{d}A}{\mathrm{d}\theta}=0\) when \(6\cos^{2}\theta+4\cos\theta-3=0\).

(2)
(d)

Hence find the value of \(\theta\) for which the area of the cross-section is a maximum, and find this maximum area.

(3)
(e)

Find the percentage by which this maximum area exceeds the area of the cross-section when the sides are vertical.

(2)
Show mark scheme
WorkingMarkNotes
(a)
height \(=15\sin\theta\)A1
width of the top \(=20+2(15\cos\theta)=20+30\cos\theta\)A1
\(A=\tfrac12\big(20+(20+30\cos\theta)\big)\times15\sin\theta=(20+15\cos\theta)\,15\sin\theta\)M1Use of the trapezium area formula with their lengths.
\(A=300\sin\theta+225\sin\theta\cos\theta\)AG
(b)
\(300\cos\theta\)A1
attempt to use the product rule on \(\sin\theta\cos\theta\)M1
\(225\left(\cos^{2}\theta-\sin^{2}\theta\right)\)A1\(\dfrac{\mathrm{d}A}{\mathrm{d}\theta}=300\cos\theta+225\left(\cos^{2}\theta-\sin^{2}\theta\right)\). Accept \(225\cos2\theta\).
(c)
use of \(\sin^{2}\theta=1-\cos^{2}\theta\): \(300\cos\theta+225(2\cos^{2}\theta-1)=0\)M1
\(450\cos^{2}\theta+300\cos\theta-225=0\), then divide by 75A1
\(6\cos^{2}\theta+4\cos\theta-3=0\)AG
(d)
\(\cos\theta=0.448\), rejecting \(\cos\theta=-1.11\)A1\(\cos\theta=\dfrac{-2+\sqrt{22}}{6}=0.448402\ldots\); the other root is less than \(-1\).
\(\theta=1.11\)A1\(1.10581\ldots\) radians. Accept \(63.4^{\circ}\).
\(A=358\ \text{cm}^{2}\)A1\(358.328\ldots\) Accept GDC maximum of \(A\) directly.
(e)
area with vertical sides \(=300\ \text{cm}^{2}\)A1\(\theta=\tfrac{\pi}{2}\).
\(19.4\%\)A1\(19.4429\ldots\%\)

Answers: (b) \(300\cos\theta+225(\cos^{2}\theta-\sin^{2}\theta)\) · (d) \(\theta=1.11\), \(A=358\ \text{cm}^{2}\) · (e) 19.4%

116AASL5-q00875.9 Kinematics Paper 2Hard10 marks

Two particles, P and Q, leave a fixed point O at the same time, \(t=0\), and move along the same straight line. The velocity of P, \(v_{\text{P}}\ \text{m s}^{-1}\), after \(t\) seconds is given by \(v_{\text{P}}(t)=10\sin(0.8t)\,\mathrm{e}^{-0.2t}\), for \(0\le t\le 8\). Particle Q moves with a constant velocity of \(2\ \text{m s}^{-1}\).

(a)

Find the value of \(t\) at which P first changes direction.

(2)
(b)

Find the total distance travelled by P in the 8 seconds.

(2)
(c)

Determine whether P is speeding up or slowing down when \(t=5\). Justify your answer.

(3)
(d)

Find the values of \(t\), for \(0\lt t\le 8\), at which P and Q are at the same position.

(3)
Show mark scheme
WorkingMarkNotes
(a)
\(\sin(0.8t)=0\), or first zero of \(v_{\text{P}}\) after \(t=0\) on the GDC(M1)
\(t=3.93\)A1\(\tfrac{5\pi}{4}=3.92699\ldots\)
(b)
\(\displaystyle\int_{0}^{8}|v_{\text{P}}(t)|\,\mathrm{d}t\)(M1)Or \(17.1286\ldots+7.80962\ldots+0.0173679\ldots\), split at \(t=\tfrac{5\pi}{4}\) and \(t=\tfrac{5\pi}{2}\).
\(25.0\) mA1\(24.9556\ldots\) Accept \(24.9\) to \(25.0\). Award A0 for \(9.34\) (the displacement).
(c)
attempt to find \(v_{\text{P}}(5)\) and \(a_{\text{P}}(5)=v_{\text{P}}'(5)\)M1
\(v_{\text{P}}(5)=-2.78\) and \(a_{\text{P}}(5)=-1.37\)A1\(-2.78412\ldots\) and \(-1.36687\ldots\)
velocity and acceleration have the same sign, so P is speeding upR1Do not award R1 without the A1 values (or their signs) seen.
(d)
\(\displaystyle\int_{0}^{t}v_{\text{P}}(u)\,\mathrm{d}u=2t\)M1Equating the displacement of P with the displacement of Q; e.g. graphs of both displacements on the GDC.
\(t=0.546\)A1\(0.546089\ldots\)
\(t=6.07\)A1\(6.06781\ldots\)

Answers: (a) \(t=3.93\) · (b) 25.0 m · (c) speeding up · (d) \(t=0.546,\ 6.07\)

117AASL5-q00885.9 Kinematics Paper 2Hard9 marks

A particle starts from a fixed point O and moves in a straight line. Its velocity, \(v\ \text{m s}^{-1}\), after \(t\) seconds is given by \(v(t)=5-t\,\mathrm{e}^{0.4t}\), for \(t\ge0\). The particle first moves away from O, then turns and returns to O.

(a)

Find the value of \(t\) at which the particle turns.

(2)
(b)

Find the greatest distance of the particle from O before it returns.

(2)
(c)

Find the time at which the particle returns to O.

(3)
(d)

Find the speed of the particle when it returns to O.

(2)
Show mark scheme
WorkingMarkNotes
(a)
\(5-t\,\mathrm{e}^{0.4t}=0\)(M1)
\(t=2.13\)A1\(2.13151\ldots\)
(b)
\(\displaystyle\int_{0}^{2.13151\ldots}v(t)\,\mathrm{d}t\)(M1)FT from (a).
\(6.57\) mA1\(6.56851\ldots\)
(c)
\(\displaystyle\int_{0}^{T}v(t)\,\mathrm{d}t=0\)M1Displacement equal to zero; accept use of a graph of the displacement function.
\(T\gt 2.13\) (rejects \(T=0\))(A1)
\(T=3.61\) sA1\(3.61393\ldots\)
(d)
\(|v(3.61393\ldots)|\)(M1)
\(10.3\ \text{m s}^{-1}\)A1\(v=-10.3386\ldots\) Award A0 for \(-10.3\).

Answers: (a) \(t=2.13\) · (b) 6.57 m · (c) \(t=3.61\) s · (d) \(10.3\ \text{m s}^{-1}\)

118AASL5-q00915.9 Kinematics Paper 2Hard15 marks

A particle P moves in a straight line, starting from a fixed point O. Its velocity, \(v\ \text{m s}^{-1}\), after \(t\) seconds is given by \(v(t)=12t\,\mathrm{e}^{-0.5t}-3\), for \(0\le t\le10\). The graph of \(v\) is shown below.

tvO10−3
(a)

Write down the initial speed of P.

(1)
(b)

Find the maximum velocity of P.

(2)
(c)

Find the values of \(t\) at which P changes direction.

(2)
(d)

Find the acceleration of P when \(t=1\).

(2)
(e)

Determine whether P is speeding up or slowing down when \(t=7\). Justify your answer.

(2)
(f)

Find the total distance travelled by P in the 10 seconds.

(3)
(g)

Find the greatest distance of P from O during the 10 seconds.

(3)
Show mark scheme
WorkingMarkNotes
(a)
\(3\ \text{m s}^{-1}\)A1Award A0 for \(-3\).
(b)
use of GDC to find the maximum of \(v\) (at \(t=2\))(M1)
\(5.83\ \text{m s}^{-1}\)A1\(5.82910\ldots\ (=24\mathrm{e}^{-1}-3)\)
(c)
\(v(t)=0\), e.g. zeros on graph(M1)
\(t=0.289\) and \(t=6.52\)A1\(0.288842\ldots\), \(6.52337\ldots\)
(d)
\(a=v'(1)\), e.g. GDC derivative, or \(a=12\mathrm{e}^{-0.5t}-6t\mathrm{e}^{-0.5t}\)(M1)
\(3.64\ \text{m s}^{-2}\)A1\(3.63918\ldots\)
(e)
\(v(7)=-0.463\lt 0\) and \(a(7)=-0.906\lt 0\); velocity and acceleration have the same signR1\(v(7)=-0.463419\ldots\), \(a(7)=-0.905921\ldots\)
speeding upA1Award A1 only if R1 is awarded.
(f)
\(\displaystyle\int_{0}^{10}\left|12t\,\mathrm{e}^{-0.5t}-3\right|\mathrm{d}t\)(M1)Must see an absolute value or the integral split at the times found in (c).
\(0.41163+21.0020+4.53088\)(A1)Areas of the three parts (seen or implied).
\(25.9\) mA1\(25.9444\ldots\)
(g)
displacement \(s(t)=\displaystyle\int_{0}^{t}v\,\mathrm{d}u\), considered at the turning times and at \(t=10\)(M1)
\(s(0.289)=-0.412\), \(s(6.52)=20.6\), \(s(10)=16.1\)(A1)\(20.5903\ldots\), \(16.0595\ldots\)
\(20.6\) mA1

Answers: (a) \(3\ \text{m s}^{-1}\) · (b) \(5.83\ \text{m s}^{-1}\) · (c) \(t=0.289,\ 6.52\) · (d) \(3.64\ \text{m s}^{-2}\) · (e) speeding up · (f) 25.9 m · (g) 20.6 m

119AASL5-q00925.9 Kinematics Paper 2Hard15 marks

A train leaves station A from rest at time \(t=0\) and travels along a straight track to station B, where it stops. Its velocity, \(v\ \text{m s}^{-1}\), \(t\) seconds after leaving A is modelled by \(v(t)=0.0005\,t^{2}(60-t)\), for \(0\le t\le60\).

(a)

Find the maximum velocity of the train.

(2)
(b)

Find the distance between station A and station B.

(2)
(c)

Find the maximum acceleration of the train.

(2)
(d)

Find the time taken for the train to travel half of the distance from A to B.

(3)
(e)

At \(t=0\), a cyclist passes station A riding at a constant velocity of \(8\ \text{m s}^{-1}\) in the same direction as the train. Find the time at which the train catches up with the cyclist, and the distance from A at which this happens.

(3)
(f)

Find the greatest distance between the cyclist and the train before the train catches up with the cyclist.

(3)
Show mark scheme
WorkingMarkNotes
(a)
\(v'(t)=0\), or maximum on the graph of \(v\)(M1)\(v'(t)=0.06t-0.0015t^{2}=0\Rightarrow t=40\)
\(16\ \text{m s}^{-1}\)A1
(b)
\(\displaystyle\int_{0}^{60}0.0005\,t^{2}(60-t)\,\mathrm{d}t\)(M1)
\(540\) mA1
(c)
\(a(t)=0.06t-0.0015t^{2}\), maximum where \(a'(t)=0\), i.e. \(t=20\); or maximum of the graph of \(v'\)(M1)
\(0.6\ \text{m s}^{-2}\)A1Award A0 for \(1.8\) or \(-1.8\) (the deceleration at \(t=60\)).
(d)
\(\displaystyle\int_{0}^{T}v(t)\,\mathrm{d}t=270\)M1FT from (b).
\(\dfrac{T^{3}}{100}-\dfrac{T^{4}}{8000}=270\), or graph of the integral(A1)
\(T=36.9\) sA1\(36.8563\ldots\)
(e)
\(\displaystyle\int_{0}^{t}v(u)\,\mathrm{d}u=8t\)M1Equating the distances travelled.
\(t=40\) sA1Other solutions of \(t^{3}-80t^{2}+64\,000=0\) are outside \(0\lt t\le 60\).
\(320\) mA1
(f)
the gap \(8t-s(t)\) is greatest when the velocities are equal, \(v(t)=8\)R1Or attempt to maximize the gap with technology.
\(t=20\)A1The other solution, \(t=54.6\), is after the train has caught up.
\(8(20)-60=100\) mA1\(s(20)=60\).

Answers: (a) \(16\ \text{m s}^{-1}\) · (b) 540 m · (c) \(0.6\ \text{m s}^{-2}\) · (d) 36.9 s · (e) \(t=40\) s, 320 m from A · (f) 100 m

120AASL5-q01205.11 Definite integrals and areas Paper 2Hard15 marks

At 00:00 a tank holds 2000 litres of water. For the next 24 hours, water flows into the tank at a rate of \(R(t)=60t\,\mathrm{e}^{-0.25t}\) litres per hour, where \(t\) is the time in hours after 00:00. At the same time, water is pumped out of the tank at a constant rate of 30 litres per hour.

(a)

Find the maximum rate at which water flows into the tank.

(2)
(b)

Find the total volume of water that flows into the tank during the 24 hours.

(2)
(c)

Find the values of \(t\) at which the rate of inflow is equal to the rate of outflow.

(2)
(d)

Explain why the volume of water in the tank is greatest when \(t\) is equal to the larger of your values in part (c).

(2)
(e)

Find the greatest volume of water in the tank during the 24 hours. Give your answer to the nearest litre.

(3)
(f)

Find the volume of water in the tank at the end of the 24 hours. Give your answer to the nearest litre.

(2)
(g)

Find the least volume of water in the tank during the 24 hours. Give your answer to the nearest litre.

(2)
Show mark scheme
WorkingMarkNotes
(a)
maximum of \(R\) on GDC, or \(R'(t)=0\Rightarrow t=4\)(M1)
\(88.3\) litres per hourA1\(88.2910\ldots\ (=240\mathrm{e}^{-1})\)
(b)
\(\displaystyle\int_{0}^{24}60t\,\mathrm{e}^{-0.25t}\,\mathrm{d}t\)(M1)
\(943\) litresA1\(943.342\ldots\)
(c)
\(60t\,\mathrm{e}^{-0.25t}=30\)(M1)
\(t=0.578\) and \(t=13.0\)A1\(0.577685\ldots\), \(13.0467\ldots\)
(d)
for \(0.578\lt t\lt 13.0\), \(R(t)\gt 30\), so the volume is increasingR1
for \(13.0\lt t\le 24\), \(R(t)\lt 30\), so the volume is decreasingR1Must refer to the comparison of rates on both sides of \(t=13.0\). The volume also decreases for \(0\lt t\lt 0.578\), but only by about 8 litres, so \(V(13.0)\gt V(0)\).
(e)
\(V=2000+\displaystyle\int_{0}^{13.0467}\big(R(t)-30\big)\,\mathrm{d}t\)(M1)
\(\displaystyle\int_{0}^{13.0467}\big(R(t)-30\big)\,\mathrm{d}t=411.807\ldots\)(A1)
\(2412\) litresA1\(2411.81\ldots\) Award A0 for 2410 (not to the nearest litre).
(f)
\(2000+943.342-24\times30\)(M1)FT from (b).
\(2223\) litresA1\(2223.34\ldots\)
(g)
\(2000+\displaystyle\int_{0}^{0.577685}\big(R(t)-30\big)\,\mathrm{d}t\)(M1)Must consider the smaller time found in (c); \(V(24)\gt 2000\).
\(1992\) litresA1\(1991.77\ldots\)

Answers: (a) 88.3 L h−1 · (b) 943 L · (c) \(t=0.578,\ 13.0\) · (e) 2412 L · (f) 2223 L · (g) 1992 L