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Edexcel International A Level Maths · P2 · Pure Mathematics 2

Proof and algebraic division

28 free, high-quality past-paper-style questions on Proof and algebraic division for Edexcel IAL Maths, each with a full mark scheme. For when you have finished the past papers, or want to practise one topic at a time.IAL Maths notes and flashcards →Not sure of your level? Diagnostic test →Multiple choice or structured questions, with the mark scheme as a separate PDF.28 new this month · 233 marks · Updated 26 October 2026 · Created by Evan Kotronis with AI assistance · How questions are checked

1IALM-P2-1-B-01 P2 · ASEasy5 marks

In this question, m and n are integers, and you may use the fact that an integer is even if it can be written as 2 × (an integer) and odd if it can be written as 2 × (an integer) + 1.

(a)

Prove that the product of any two odd numbers is odd.

(3)
(b)

Prove that the sum of any even number and any odd number is odd.

(2)
Show mark scheme
AnswerMarkNotes
Part (a)
let the odd numbers be 2m + 1 and 2n + 1 (different letters, so any two odd numbers are covered)B1
(2m + 1)(2n + 1) = 4mn + 2m + 2n + 1M1
= 2(2mn + m + n) + 1, which is 2 × an integer + 1, so the product is oddA1
Part (b)
2m + (2n + 1) = 2(m + n) + 1M1
m + n is an integer, so the sum is 2 × an integer + 1, which is oddA1

Common error: Writing both odd numbers as 2n + 1. That only proves the result for an odd number multiplied by itself — use two different letters.

2IALM-P2-1-B-02 P2 · ASEasy6 marks

f(x) = x3 + 3x2 − 10x − 24

(a)

Use the factor theorem to show that (x + 2) is a factor of f(x).

(2)
(b)

Factorise f(x) completely.

(3)
(c)

Hence solve f(x) = 0.

(1)
Show mark scheme
AnswerMarkNotes
Part (a)
f(−2) = (−2)3 + 3(−2)2 − 10(−2) − 24 = −8 + 12 + 20 − 24M1
= 0, so (x + 2) is a factorA1
Part (b)
divides by (x + 2) or compares coefficients to obtain a quadratic factor x2 + cx − 12M1
x2 + x − 12A1
f(x) = (x + 2)(x + 4)(x − 3)A1
Part (c)
x = −4, x = −2, x = 3 (ft from their three linear factors)B1

Exam tip: In a “show that” part, write every substituted value and the total 0, then a conclusion. The answer is given, so the working is what counts.

3IALM-P2-1-B-03 P2 · ASEasy7 marks

g(x) = 2x3 − x2 + 4x − 5, for all real values of x.

(a)

Find the remainder when g(x) is divided by (x − 2).

(2)
(b)

Find the remainder when g(x) is divided by (2x + 1).

(2)
(c)

Show that (x − 1) is a factor of g(x).

(1)
(d)

Hence show that the equation g(x) = 0 has exactly one real root.

(2)
Show mark scheme
AnswerMarkNotes
Part (a)
g(2) = 16 − 4 + 8 − 5M1
remainder = 15A1
Part (b)
g(−½) = 2(−⅛) − ¼ + 4(−½) − 5 = −¼ − ¼ − 2 − 5M1
remainder = −15/2 (−7.5)A1
Part (c)
substituting x = 1: 2 − 1 + 4 − 5 = 0, so (x − 1) is a factor by the factor theoremB1
Part (d)
g(x) = (x − 1)(2x2 + x + 5)M1
discriminant of 2x2 + x + 5 is 12 − 4(2)(5) = −39 < 0, so the quadratic has no real roots and the only real root is x = 1A1

Common error: Substituting x = 1 or x = −1 for the divisor (2x + 1). The divisor is zero when x = −½, so the remainder is g(−½).

4IALM-P2-1-B-04 P2 · ASEasy6 marks

Each of the following statements is false. For each one, give a counterexample and show clearly why it disproves the statement.

(a)

For every real number x, x2 ≥ x.

(2)
(b)

The sum of any two irrational numbers is irrational.

(2)
(c)

If p is a prime number, then 2p + 1 is also prime.

(2)
Show mark scheme
AnswerMarkNotes
Part (a)
for example x = ½: x2 = ¼M1
¼ < ½, so x2 < x and the statement is falseA1
Part (b)
for example √3 and −√3 (or 2 + √5 and 2 − √5), which are both irrationalM1
their sum is 0 (or 4), which is rational, so the statement is falseA1
Part (c)
for example p = 7 (prime): 2 × 7 + 1 = 15M1
15 = 3 × 5 is not prime, so the statement is false (accept p = 13, 17, 19, … with a correct factorisation)A1

Exam tip: A counterexample needs three things: the specific value, the calculation showing the statement fails, and a sentence saying the statement is false.

5IALM-P2-1-FB-01 P2 · ASEasy7 marks

Figure 1 shows part of the curve with equation y = f(x), where f(x) = x3 + ax2 − 10x + 8 and a is a constant. The curve crosses the x-axis at the point A(−4, 0) and at the points P and Q.

−4−3−2−1123−24−16−881624xyOA(−4, 0)PQy = f(x)
(a)

Use the point A to show that a = 1.

(2)
(b)

Factorise f(x) completely.

(3)
(c)

Write down the x-coordinates of P and Q.

(1)
(d)

Find the remainder when f(x) is divided by (x + 1).

(1)
Show mark scheme
AnswerMarkNotes
Part (a)
f(−4) = 0: (−4)3 + a(−4)2 − 10(−4) + 8 = 0M1
−64 + 16a + 40 + 8 = 16a − 16 = 0, so a = 1A1
Part (b)
(x + 4) is a factor; divides x3 + x2 − 10x + 8 by (x + 4) or compares coefficientsM1
quadratic factor x2 − 3x + 2A1
f(x) = (x + 4)(x − 1)(x − 2)A1
Part (c)
P: x = 1 and Q: x = 2 (ft their factors)B1
Part (d)
f(−1) = −1 + 1 + 10 + 8 = 18B1

Common error: Reading A(−4, 0) as a sign that (x − 4) is a factor. A root at x = −4 gives the factor (x + 4), because x + 4 = 0 when x = −4.

6IALM-P2-1-FB-02 P2 · ASEasy7 marks

Figure 1 shows part of the curve with equation y = g(x), where g(x) = x3 − 4x2 + x + 6. The point D(4, 10) lies on the curve, and the curve crosses the x-axis at three points whose x-coordinates are integers.

−11234−8−448121620xyOD(4, 10)y = g(x)
(a)

Using the point D and the remainder theorem, write down the remainder when g(x) is divided by (x − 4).

(2)
(b)

Use algebraic long division to divide g(x) by (x − 4). State the quotient and confirm the remainder.

(3)
(c)

Use the factor theorem to show that (x − 3) is a factor of g(x). Hence, using Figure 1, write g(x) as a product of three linear factors.

(2)
Show mark scheme
AnswerMarkNotes
Part (a)
by the remainder theorem the remainder is g(4)M1
D(4, 10) lies on the curve, so g(4) = 10: remainder = 10A1
Part (b)
first term x2: (x3 − 4x2) − (x3 − 4x2) = 0, bring down x + 6M1
next terms 0x and + 1: (x + 6) − (x − 4) = 10A1
quotient x2 + 1, remainder 10, so g(x) = (x − 4)(x2 + 1) + 10A1
Part (c)
g(3) = 27 − 36 + 3 + 6 = 0, so (x − 3) is a factorB1
the curve also crosses the axis at x = −1 and x = 2: g(x) = (x + 1)(x − 2)(x − 3)B1

Exam tip: When a power is missing from the quotient, write it with a zero coefficient (x2 + 0x + 1) so that like terms stay lined up in the division.

7IALM-P2-1-FB-03 P2 · ASEasy6 marks

Figure 1 shows two fair spinners, P and Q. In a game, each spinner is spun once and the two numbers obtained are recorded.

1346Spinner P257Spinner Q
(a)

Prove, by exhaustion, that the product of the two numbers can never be a square number.

(3)
(b)

Ravi claims that the sum of the two numbers is always odd. Show that Ravi’s claim is false.

(2)
(c)

Explain why the method used in part (a) could not be used to prove a statement about the products of all pairs of positive integers.

(1)
Show mark scheme
AnswerMarkNotes
Part (a)
all 4 × 3 = 12 combinations consideredM1
products: 2, 5, 7, 6, 15, 21, 8, 20, 28, 12, 30, 42A1
the square numbers up to 42 are 1, 4, 9, 16, 25, 36 and none of them appears, so the product is never a square numberA1
Part (b)
e.g. 1 on P and 5 on Q: 1 + 5 = 6M1
6 is even, so the claim is false (accept 1 + 7, 3 + 5, 3 + 7, 4 + 2 or 6 + 2)A1
Part (c)
there are infinitely many pairs of positive integers, so they cannot all be checked one at a timeB1

Exam tip: Set the cases out in a table so that it is clear none is missing, then finish with a sentence that links the checked cases to the claim.

8IALM-P2-1-FB-04 P2 · ASEasy5 marks

Figure 1 shows the graphs of y = 2x and y = x2 for 0 ≤ x ≤ 5. The curves meet at the points (2, 4) and (4, 16).

1234548121620242832xyO(2, 4)(4, 16)y = 2ˣy = x²
(a)

Claim 1: “2x ≥ x2 for every positive number x.” Use Figure 1 to choose a suitable value of x, and show that Claim 1 is false.

(2)
(b)

Claim 2: “the only positive value of x for which 2x = x2 is x = 2.” Show that Claim 2 is false.

(2)
(c)

A student says: “Figure 1 shows that 2x > x2 for every x > 4, so this is proved.” Explain why the figure alone is not a proof.

(1)
Show mark scheme
AnswerMarkNotes
Part (a)
the figure shows 2x below x2 between x = 2 and x = 4; choose e.g. x = 3M1
23 = 8 and 32 = 9, and 8 < 9, so Claim 1 is false (accept any x with 2 < x < 4 and correct values)A1
Part (b)
x = 4: 24 = 16 and 42 = 16M1
so 2x = x2 at x = 4 as well, and Claim 2 is falseA1
Part (c)
the figure only shows values up to x = 5 and its readings are approximate; a proof must establish the result for every x > 4B1

Common error: Giving a counterexample without the arithmetic. Write both values, 23 = 8 and 32 = 9, compare them, and state that the claim is false.

9IALM-P2-1-B-05 P2 · ASMedium7 marks

This question is about the remainders left when whole numbers are divided by 3. Throughout, n is an integer.

(a)

Prove, by exhaustion, that n2 leaves a remainder of 0 or 1 when it is divided by 3.

(4)
(b)

Hence prove that n2 + 1 is never a multiple of 3.

(2)
(c)

A student claims that n2 + 2 is also never a multiple of 3. Show that the student is wrong.

(1)
Show mark scheme
AnswerMarkNotes
Part (a)
every integer can be written as 3k, 3k + 1 or 3k + 2 for some integer k, so these three cases cover all integersB1
squares at least one non-zero case correctly, e.g. (3k + 1)2 = 9k2 + 6k + 1M1
(3k)2 = 3(3k2); (3k + 1)2 = 3(3k2 + 2k) + 1; (3k + 2)2 = 9k2 + 12k + 4 = 3(3k2 + 4k + 1) + 1A1
remainders are 0, 1 and 1, so in every case the remainder is 0 or 1A1
Part (b)
by (a), n2 + 1 leaves a remainder of 0 + 1 = 1 or 1 + 1 = 2 when divided by 3M1
the remainder is never 0, so n2 + 1 is never a multiple of 3A1
Part (c)
n = 1 gives 1 + 2 = 3, which is a multiple of 3, so the claim is false (any n not a multiple of 3 works)B1

Exam tip: Say why your cases cover everything (“every integer is 3k, 3k + 1 or 3k + 2”) and finish with a conclusion that brings all the cases together.

10IALM-P2-1-B-06 P2 · ASMedium6 marks

The expression E is defined for all real values of x by E = 4x2 − 12x + 13.

(a)

Write E in the form (2x + p)2 + q, where p and q are constants to be found.

(2)
(b)

Hence prove that E > 0 for all real values of x.

(2)
(c)

Find the greatest value of 1/E, and the value of x at which it occurs.

(2)
Show mark scheme
AnswerMarkNotes
Part (a)
(2x − 3)2 + q, so p = −3B1
(2x − 3)2 = 4x2 − 12x + 9, so q = 13 − 9 = 4: E = (2x − 3)2 + 4B1
Part (b)
(2x − 3)2 ≥ 0 for all real xM1
so E = (2x − 3)2 + 4 ≥ 4 > 0, hence E > 0 for all real xA1
Part (c)
least value of E is 4, so greatest value of 1/E is ¼ (ft their q)B1
when 2x − 3 = 0, i.e. x = 3/2 (ft their p)B1

Common error: Concluding E &gt; 0 from “(2x − 3)² &gt; 0”. A square can equal 0, so write ≥ 0 and let the + 4 make the expression strictly positive.

11IALM-P2-1-B-07 P2 · ASMedium8 marks

A cubic polynomial is defined by h(x) = 6x3 − x2 − 5x + 7. In this question you divide it by a linear expression whose leading coefficient is not 1.

(a)

Use algebraic long division to find the quotient and the remainder when h(x) is divided by (3x − 2).

(4)
(b)

Use the remainder theorem to verify your remainder.

(2)
(c)

Hence factorise h(x) − 5 completely.

(2)
Show mark scheme
AnswerMarkNotes
Part (a)
long division with first term 2x2 and a subtraction carried out: 6x3 − x2 − (6x3 − 4x2) = 3x2M1
second term + x: 3x2 − 5x − (3x2 − 2x) = −3xA1
third term −1: −3x + 7 − (−3x + 2) = 5, so quotient 2x2 + x − 1A1
remainder 5A1
Part (b)
h(⅔) = 6(8/27) − 4/9 − 10/3 + 7M1
= 16/9 − 4/9 − 30/9 + 63/9 = 45/9 = 5 ✓A1
Part (c)
h(x) − 5 = (3x − 2)(2x2 + x − 1) (ft their quotient)M1
= (3x − 2)(2x − 1)(x + 1)A1

Exam tip: Line up like powers in long division and put every subtraction in brackets. A sign slip in the first subtraction spoils every later line.

12IALM-P2-1-B-08 P2 · ASMedium7 marks

The curve C has equation y = p(x), where p(x) = 2x3 + kx2 − 11x − 6 and k is a constant. One of the factors of p(x) is (x + 3).

(a)

Find the value of k.

(2)
(b)

Factorise p(x) completely.

(3)
(c)

Hence write down the coordinates of the points where C meets the coordinate axes.

(2)
Show mark scheme
AnswerMarkNotes
Part (a)
p(−3) = −54 + 9k + 33 − 6 = 0M1
9k = 27, k = 3A1
Part (b)
p(x) = (x + 3)(2x2 + cx − 2), from division or comparing coefficientsM1
(x + 3)(2x2 − 3x − 2)A1
= (x + 3)(2x + 1)(x − 2)A1
Part (c)
(−3, 0), (−½, 0) and (2, 0) (ft their factors)B1
(0, −6)B1

Model sketch

OxyC(−3, 0)(−½, 0)(2, 0)(0, −6)
Figure: model sketch of C (k = 3) with its axis intercepts

Common error: Using the remainder theorem with the wrong sign: (x + 3) is a factor when p(−3) = 0, not p(3).

13IALM-P2-1-B-09 P2 · ASMedium8 marks

The polynomial q(x) = x3 + ax2 + bx + 10 has unknown constants a and b. Dividing q(x) by (x − 2) leaves no remainder, while dividing q(x) by (x + 1) leaves a remainder of 24.

(a)

Find the values of a and b.

(5)
(b)

Hence factorise q(x) completely.

(3)
Show mark scheme
AnswerMarkNotes
Part (a)
q(2) = 0: 8 + 4a + 2b + 10 = 0M1
q(−1) = 24: −1 + a − b + 10 = 24M1
2a + b = −9 and a − b = 15A1
solves simultaneously, e.g. adding: 3a = 6M1
a = 2, b = −13A1
Part (b)
divides by (x − 2) to get a quadratic factorM1
x2 + 4x − 5A1
q(x) = (x − 2)(x − 1)(x + 5)A1

Exam tip: Turn each sentence of information into one equation before solving: “no remainder” means q(2) = 0, “remainder 24” means q(−1) = 24.

14IALM-P2-1-B-10 P2 · ASMedium7 marks

A puzzle book makes two claims about whole numbers. Prove each claim.

(a)

The difference between the squares of any two consecutive odd numbers is a multiple of 8.

(4)
(b)

The sum of the squares of any three consecutive integers is never a multiple of 3.

(3)
Show mark scheme
AnswerMarkNotes
Part (a)
let the numbers be 2n + 1 and 2n + 3, where n is an integerB1
(2n + 3)2 − (2n + 1)2 = (4n2 + 12n + 9) − (4n2 + 4n + 1)M1
= 8n + 8A1
= 8(n + 1), which is 8 × an integer, so the difference is a multiple of 8A1
Part (b)
(n − 1)2 + n2 + (n + 1)2 (or n2 + (n + 1)2 + (n + 2)2)M1
= 3n2 + 2 (or 3n2 + 6n + 5 = 3(n2 + 2n + 1) + 2)A1
this is 3 × an integer + 2, so it leaves remainder 2 on division by 3 and is never a multiple of 3A1

Exam tip: Choosing the middle number as n, so the three integers are n − 1, n and n + 1, makes the algebra shorter because the linear terms cancel.

15IALM-P2-1-FB-05 P2 · ASMedium8 marks

Figure 1 shows a large square made from four congruent right-angled triangles and a smaller square. Each triangle has shorter sides of lengths a and b and a hypotenuse of length c, where a, b and c are positive.

ababababcccc
(a)

By finding the area of the large square in two different ways, prove that a2 + b2 = c2.

(4)
(b)

Hence prove that a + b ≤ √2 c.

(3)
(c)

State the condition on a and b for which a + b = √2 c, and describe the triangles in Figure 1 in this case.

(1)
Show mark scheme
AnswerMarkNotes
Part (a)
the large square has side a + b, so its area is (a + b)2B1
it is also the inner square plus four triangles: c2 + 4 × ½abM1
a2 + 2ab + b2 = c2 + 2abM1
subtracting 2ab: a2 + b2 = c2A1
Part (b)
(a − b)2 ≥ 0, so a2 + b2 ≥ 2abM1
(a + b)2 = a2 + b2 + 2ab ≤ 2(a2 + b2) = 2c2M1
a + b > 0 and c > 0, so taking square roots: a + b ≤ √2 cA1
Part (c)
a = b: the four triangles are then isosceles right-angled trianglesB1

Exam tip: Taking square roots keeps the direction of an inequality only when both sides are non-negative. Say that a + b &gt; 0 and c &gt; 0 before you do it.

16IALM-P2-1-FB-06 P2 · ASMedium8 marks

Figure 1 shows a cuboid. The lengths of two of its edges, in centimetres, are shown in terms of x, and the third edge has length d cm. The volume of the cuboid is V cm3, where V = 2x3 + 9x2 + 7x − 6.

(2x − 1) cm(x + 3) cmd cmNot drawn to scale
(a)

Use algebraic division to show that d = x + 2.

(3)
(b)

Explain why x > ½.

(1)
(c)

Given that V = 150, show that x = 3 is a solution of 2x3 + 9x2 + 7x − 156 = 0, and prove that it is the only real solution.

(3)
(d)

Find the dimensions of the cuboid when its volume is 150 cm³.

(1)
Show mark scheme
AnswerMarkNotes
Part (a)
divides 2x3 + 9x2 + 7x − 6 by (x + 3) (or by (2x − 1))M1
quotient 2x2 + 3x − 2 (or x2 + 5x + 6)A1
2x2 + 3x − 2 = (2x − 1)(x + 2), so V = (x + 3)(2x − 1)(x + 2) and d = x + 2A1
Part (b)
every edge length must be positive; 2x − 1 > 0 gives x > ½ (and then x + 3 and x + 2 are positive too)B1
Part (c)
2(27) + 9(9) + 7(3) − 156 = 54 + 81 + 21 − 156 = 0, so (x − 3) is a factorB1
2x3 + 9x2 + 7x − 156 = (x − 3)(2x2 + 15x + 52)M1
discriminant 152 − 4(2)(52) = 225 − 416 = −191 < 0, so the quadratic factor has no real roots and x = 3 is the only solutionA1
Part (d)
6 cm, 5 cm and 5 cmB1

Common error: Stopping as soon as x = 3 works. To show it is the only value you must deal with the quadratic factor, here by showing that its discriminant is negative.

17IALM-P2-1-FB-07 P2 · ASMedium8 marks

Figure 1 shows the curve with equation y = f(x), where f(x) = x3 + ax2 + bx + c and a, b and c are constants. The curve passes through the labelled points (−2, 0), (1, 0) and (0, −8), and crosses the x-axis again at R.

−5−4−3−2−112−16−12−8−44812162024xyO(−2, 0)(1, 0)(0, −8)Ry = f(x)
(a)

Write down the value of c.

(1)
(b)

Find the value of a and the value of b.

(4)
(c)

Find the x-coordinate of R.

(2)
(d)

Find the remainder when f(x) is divided by (x − 2).

(1)
Show mark scheme
AnswerMarkNotes
Part (a)
the curve meets the y-axis at (0, −8), so c = −8B1
Part (b)
x = −2: −8 + 4a − 2b − 8 = 0, giving 2a − b = 8M1
x = 1: 1 + a + b − 8 = 0, giving a + b = 7M1
solves simultaneously, e.g. adding: 3a = 15M1
a = 5, b = 2A1
Part (c)
divides x3 + 5x2 + 2x − 8 by (x + 2): x2 + 3x − 4 = (x − 1)(x + 4)M1
R: x = −4A1
Part (d)
f(2) = 8 + 20 + 4 − 8 = 24B1

Exam tip: Every labelled point on a curve gives one equation. A point on the y-axis gives the constant term straight away, which leaves fewer unknowns for the other points.

18IALM-P2-1-FB-08 P2 · ASMedium9 marks

Figure 1 shows the integers from 1 to 36 written in six columns. The column headings describe the numbers in each column, where k is an integer (k = 0 in the first row). The prime numbers are circled.

6k + 16k + 26k + 36k + 46k + 56k + 6123456789101112131415161718192021222324252627282930313233343536circled numbers are prime
(a)

Using Figure 1, state the two columns that contain the primes greater than 3.

(1)
(b)

Prove, by exhaustion, that every prime number greater than 3 is of the form 6k + 1 or 6k + 5, where k is an integer.

(4)
(c)

Show that the statement “every number of the form 6k + 1, where k ≥ 1, is prime” is false.

(2)
(d)

Prove that, if p is a prime number greater than 3, then p2 − 1 is a multiple of 12.

(2)
Show mark scheme
AnswerMarkNotes
Part (a)
6k + 1 and 6k + 5B1
Part (b)
every integer can be written as 6k, 6k + 1, 6k + 2, 6k + 3, 6k + 4 or 6k + 5B1
6k = 2(3k), 6k + 2 = 2(3k + 1) and 6k + 4 = 2(3k + 2) are multiples of 2M1
6k + 3 = 3(2k + 1) is a multiple of 3M1
a multiple of 2 or of 3 that is greater than 3 is not prime, so a prime greater than 3 must be of the form 6k + 1 or 6k + 5A1
Part (c)
25 = 6(4) + 1 is of this formM1
25 = 5 × 5 is not prime, so the statement is false (accept 49 = 6(8) + 1 = 7 × 7, etc.)A1
Part (d)
p = 6k + 1: (6k + 1)2 − 1 = 36k2 + 12k = 12(3k2 + k)M1
p = 6k + 5: (6k + 5)2 − 1 = 36k2 + 60k + 24 = 12(3k2 + 5k + 2); in both cases p2 − 1 is 12 × an integerA1

Common error: Saying “6k + 2 is even, so it is not prime” without care: when k = 0 it equals 2, which is prime. The argument works because the claim is only about primes greater than 3.

19IALM-P2-1-FB-09 P2 · ASMedium8 marks

Figure 1 shows the curve C with equation y = 2x3 − 3x2 − 7x + 14 and the straight line L with equation y = x + 2. The line meets the curve at the points A(−2, 0) and B(2, 4), and at a third point P.

−2−112−20−16−12−8−448121620xyOA(−2, 0)B(2, 4)PCL
(a)

Show that the x-coordinates of the points where L meets C satisfy 2x3 − 3x2 − 8x + 12 = 0.

(2)
(b)

Use Figure 1 to write down one linear factor of 2x3 − 3x2 − 8x + 12, and use the factor theorem to confirm it.

(2)
(c)

Hence factorise 2x3 − 3x2 − 8x + 12 completely, and find the exact coordinates of P.

(4)
Show mark scheme
AnswerMarkNotes
Part (a)
2x3 − 3x2 − 7x + 14 = x + 2M1
2x3 − 3x2 − 8x + 12 = 0A1
Part (b)
A gives (x + 2) (or B gives (x − 2))B1
x = −2: −16 − 12 + 16 + 12 = 0 (or x = 2: 16 − 12 − 16 + 12 = 0), so it is a factorB1
Part (c)
divides by (x + 2) (or by (x − 2))M1
2x2 − 7x + 6 (or 2x2 + x − 6)A1
(x + 2)(x − 2)(2x − 3)A1
P: x = 3/2, y = 3/2 + 2 = 7/2, so P is (3/2, 7/2)A1

Exam tip: The points where a line meets a curve come from solving their equations simultaneously. Any intersection you can already see gives you a factor of the resulting cubic.

20IALM-P2-1-FB-10 P2 · ASMedium8 marks

The triangular numbers Tn are given by Tn = ½n(n + 1) for positive integers n. Figure 1 shows dot patterns for T1 to T4, and a 5 × 5 square of dots split into two triangular patterns.

T₁T₂T₃T₄5 × 5 squarenavy: 15 dotsgold: 10 dots
(a)

Explain how the 5 × 5 square in Figure 1 illustrates that T4 + T5 = 52.

(1)
(b)

Prove that Tn + Tn + 1 = (n + 1)2 for every positive integer n.

(3)
(c)

Prove that 8Tn + 1 is a perfect square for every positive integer n.

(2)
(d)

Disprove the claim “no triangular number greater than 1 is a perfect square”.

(2)
Show mark scheme
AnswerMarkNotes
Part (a)
the 25 dots split into a triangle of 10 = T4 dots and a triangle of 15 = T5 dots, so 10 + 15 = 25 = 52B1
Part (b)
Tn + 1 = ½(n + 1)(n + 2)B1
Tn + Tn + 1 = ½(n + 1)[n + (n + 2)]M1
= ½(n + 1)(2n + 2) = (n + 1)2A1
Part (c)
8Tn + 1 = 4n(n + 1) + 1 = 4n2 + 4n + 1M1
= (2n + 1)2, the square of an integerA1
Part (d)
T8 = ½ × 8 × 9 = 36M1
36 = 62 is a perfect square greater than 1, so the claim is false (accept T49 = 1225 = 352)A1

Common error: Checking a few values of n and calling it a proof. Work with a general n and simplify exactly to the target form.

21IALM-P2-1-B-11 P2 · ASHard11 marks

f(x) = 2x3 + ax2 + bx + 15, where a and b are integers.
Given that (2x − 3) is a factor of f(x), and that −49 is the remainder when f(x) is divided by (x + 2),

(a)

find the value of a and the value of b.

(5)
(b)

Factorise f(x) completely.

(3)
(c)

Hence solve the equation 2y6 − 11y4 + 2y2 + 15 = 0, giving all real solutions in exact form.

(3)
Show mark scheme
AnswerMarkNotes
Part (a)
f(3/2) = 0: 2(27/8) + a(9/4) + b(3/2) + 15 = 0M1
f(−2) = −49: −16 + 4a − 2b + 15 = −49M1
3a + 2b = −29 and 2a − b = −24 (or equivalent simplified pair)A1
solves simultaneously, e.g. b = 2a + 24 ⇒ 7a = −77M1
a = −11, b = 2A1
Part (b)
divides 2x3 − 11x2 + 2x + 15 by (2x − 3) or compares coefficientsM1
quadratic factor x2 − 4x − 5A1
f(x) = (2x − 3)(x + 1)(x − 5)A1
Part (c)
the equation is f(y2) = 0, so y2 = 3/2, −1 or 5M1
y2 = −1 has no real solutionsB1
y = ±√(3/2) = ±√6/2, y = ±√5A1

Exam tip: In a “hence” part, look for the earlier expression hiding inside the new one: here every power of y is even, so put x = y² and use the factors you already have.

22IALM-P2-1-B-12 P2 · ASHard10 marks

In this question n is an integer. Three claims are made about expressions of the form nr − ns.

(a)

Prove that n3 − n is a multiple of 6 for every integer n.

(4)
(b)

Show that the claim “n4 − n is a multiple of 4 for every integer n” is false.

(2)
(c)

Prove, by considering the cases n even and n odd, that n4 − n2 is a multiple of 4 for every integer n.

(4)
Show mark scheme
AnswerMarkNotes
Part (a)
n3 − n = n(n2 − 1) = (n − 1)n(n + 1)M1
this is the product of three consecutive integersA1
at least one of any two consecutive integers is even, so the product is a multiple of 2B1
exactly one of any three consecutive integers is a multiple of 3, so the product is a multiple of 3; being a multiple of both 2 and 3, it is a multiple of 6B1
Part (b)
n = 2: 24 − 2 = 14M1
14 is not a multiple of 4, so the claim is false (accept other valid values, e.g. n = 3 gives 78)A1
Part (c)
n4 − n2 = n2(n2 − 1)M1
n even, n = 2k: n2 = 4k2, so n2(n2 − 1) = 4k2(4k2 − 1), a multiple of 4A1
n odd, n = 2k + 1: n2 − 1 = 4k2 + 4k = 4(k2 + k), so the product is a multiple of 4A1
every integer is even or odd, so n4 − n2 is a multiple of 4 for all integers nA1

Common error: Stopping at “a product of three consecutive integers”. You must also say why such a product is divisible by 2 and by 3 to reach 6.

23IALM-P2-1-B-13 P2 · ASHard11 marks

This question develops some inequalities step by step. Each proof must start from a statement that is known to be true.

(a)

Prove that u2 + v2 ≥ 2uv for all real numbers u and v.

(2)
(b)

Hence prove that a/b + b/a ≥ 2 for all positive real numbers a and b.

(3)
(c)

Show, by means of a counterexample, that the inequality in part (b) is not true for all non-zero real numbers a and b.

(2)
(d)

Prove that x + 9/x ≥ 6 for all x > 0, and state the value of x for which equality holds.

(4)
Show mark scheme
AnswerMarkNotes
Part (a)
(u − v)2 ≥ 0 for all real u, vM1
u2 − 2uv + v2 ≥ 0, so u2 + v2 ≥ 2uvA1
Part (b)
by (a) with u = a, v = b: a2 + b2 ≥ 2abM1
a, b > 0 so ab > 0, and dividing by ab keeps the direction of the inequalityM1
a/b + b/a ≥ 2A1
Part (c)
e.g. a = 1, b = −1: a/b + b/a = −1 + (−1) = −2M1
−2 < 2, so the inequality fails for these non-zero valuesA1
Part (d)
(x − 3)2 ≥ 0 for all real xM1
x2 − 6x + 9 ≥ 0A1
x > 0, so dividing by x keeps the inequality: x − 6 + 9/x ≥ 0, i.e. x + 9/x ≥ 6A1
equality when (x − 3)2 = 0, i.e. x = 3B1

Exam tip: If you found an inequality proof by working backwards from the answer, rewrite it forwards from a true statement such as (x − 3)² ≥ 0, and say where you used positivity.

24IALM-P2-1-B-14 P2 · ASHard12 marks

A cubic function is given by f(x) = 2x3 + px2 + qx + 12, with constants p and q. The graph of y = f(x) passes through the point (2, 0). When f(x) is divided by (2x − 1), the remainder is 9.

(a)

Find the values of p and q.

(5)
(b)

Show that f(x) = (x − 2)2(2x + 3).

(3)
(c)

Write down the coordinates of the points where the graph of y = f(x) meets the x-axis, and explain why the graph touches the x-axis, without crossing it, at one of these points.

(2)
(d)

Hence find the set of values of x for which f(x) > 0.

(2)
Show mark scheme
AnswerMarkNotes
Part (a)
f(2) = 0: 16 + 4p + 2q + 12 = 0, so 2p + q = −14M1
f(½) = 9: ¼ + p/4 + q/2 + 12 = 9M1
p + 2q = −13A1
solves the pair simultaneouslyM1
p = −5, q = −4A1
Part (b)
(x − 2) is a factor as f(2) = 0; divides 2x3 − 5x2 − 4x + 12 by (x − 2)M1
quadratic factor 2x2 − x − 6A1
2x2 − x − 6 = (x − 2)(2x + 3), so f(x) = (x − 2)2(2x + 3)A1
Part (c)
(2, 0) and (−3/2, 0)B1
(x − 2) is a repeated factor and (x − 2)2 ≥ 0, so f does not change sign at x = 2: the graph touches the axis at (2, 0)B1
Part (d)
(x − 2)2 > 0 for x ≠ 2, so need 2x + 3 > 0M1
x > −3/2, x ≠ 2A1

Model sketch

Oxyy = f(x)(−3/2, 0)(2, 0)(0, 12)
Figure: model sketch: the graph crosses at (−3/2, 0) and touches at (2, 0)

Common error: Forgetting to exclude x = 2 in the last part. At a repeated root f(x) = 0, so a strict inequality f(x) &gt; 0 fails there.

25IALM-P2-1-FB-11 P2 · ASHard13 marks

f(x) = 3x3 + px2 + qx − 10, where p and q are constants.
Figure 1 shows part of the curve with equation y = f(x). The curve passes through the labelled points A(2, 0) and B(1, −16). The dashed line y = −10 meets the curve at the three points P, Q and R.

−2−112−20−16−12−8−4481216xyOy = −10A(2, 0)B(1, −16)PQRy = f(x)
(a)

Find the value of p and the value of q.

(5)
(b)

Factorise f(x) completely.

(3)
(c)

Find the remainder when f(x) is divided by (3x − 1).

(2)
(d)

Find the exact x-coordinates of P, Q and R.

(3)
Show mark scheme
AnswerMarkNotes
Part (a)
A: 24 + 4p + 2q − 10 = 0M1
B: 3 + p + q − 10 = −16M1
2p + q = −7 and p + q = −9A1
solves simultaneously, e.g. subtracting: p = 2M1
p = 2, q = −11A1
Part (b)
(x − 2) is a factor because A lies on the curve; divides 3x3 + 2x2 − 11x − 10 by (x − 2)M1
quadratic factor 3x2 + 8x + 5A1
f(x) = (x − 2)(3x + 5)(x + 1)A1
Part (c)
remainder = f(⅓) = 3(1/27) + 2(1/9) − 11/3 − 10M1
= 1/9 + 2/9 − 33/9 − 90/9 = −40/3A1
Part (d)
3x3 + 2x2 − 11x − 10 = −10, so x(3x2 + 2x − 11) = 0M1
Q: x = 0A1
x = (−2 ± √136)/6 = (−1 ± √34)/3; P is at (−1 − √34)/3 and R at (−1 + √34)/3A1

Exam tip: To find where y = f(x) meets the horizontal line y = k, solve f(x) = k. Here the constant terms cancel, so x is a common factor and one solution is x = 0.

26IALM-P2-1-FB-12 P2 · ASHard12 marks

Figure 1 shows a calendar for a month of 31 days, written in rows of seven consecutive dates. A 2 × 2 square of dates and a 3 × 3 square of dates are outlined. For any square of dates, the corner difference is defined as (top-right date × bottom-left date) − (top-left date × bottom-right date). In parts (b), (c) and (e), assume that the square lies wholly inside such a grid.

MonTueWedThuFriSatSun12345678910111213141516171819202122232425262728293031
(a)

Show that the corner difference of the outlined 2 × 2 square is 7.

(1)
(b)

Prove that the corner difference of every 2 × 2 square of dates is 7.

(3)
(c)

Prove that the corner difference of every 3 × 3 square of dates is 28.

(3)
(d)

The nine dates in the 3 × 3 square with top-left date 1 add up to 81 = 92. Use the 3 × 3 square outlined in Figure 1 to disprove the claim that the nine dates in every 3 × 3 square add up to a square number.

(2)
(e)

Prove that the corner difference of every k × k square of dates, where k ≥ 2, is 7(k − 1)2.

(3)
Show mark scheme
AnswerMarkNotes
Part (a)
10 × 16 − 9 × 17 = 160 − 153 = 7B1
Part (b)
with top-left date n, the dates are n, n + 1, n + 7 and n + 8B1
(n + 1)(n + 7) − n(n + 8) = n2 + 8n + 7 − n2 − 8nM1
= 7, whatever the value of nA1
Part (c)
corners n, n + 2, n + 14 and n + 16B1
(n + 2)(n + 14) − n(n + 16) = n2 + 16n + 28 − n2 − 16nM1
= 28A1
Part (d)
12 + 13 + 14 + 19 + 20 + 21 + 26 + 27 + 28 = 180M1
132 = 169 and 142 = 196, so 180 is not a square number and the claim is falseA1
Part (e)
corners n, n + (k − 1), n + 7(k − 1) and n + 8(k − 1)M1
[n + (k − 1)][n + 7(k − 1)] − n[n + 8(k − 1)] = n2 + 8n(k − 1) + 7(k − 1)2 − n2 − 8n(k − 1)M1
= 7(k − 1)2A1

Exam tip: Name one date n and write every other date in terms of it. Keeping (k − 1) as a single block in the last part makes the cancelling easy to see.

27IALM-P2-1-FB-13 P2 · ASHard11 marks

An open box is made from a rectangular sheet of card 16 cm by 10 cm. A square of side x cm is cut from each corner, as shown in Figure 1, and the four sides are then folded up along the dashed lines. The volume of the box is V cm3.

16 cm10 cmxxbaseNot drawn to scale
(a)

Show that V = 4x3 − 52x2 + 160x.

(2)
(b)

State the set of possible values of x.

(1)
(c)

When x = 2 the volume is 144 cm3. Show that the equation V = 144 can be written as x3 − 13x2 + 40x − 36 = 0, and use the factor theorem to show that (x − 2) is a factor of x3 − 13x2 + 40x − 36.

(2)
(d)

Factorise x3 − 13x2 + 40x − 36 completely.

(3)
(e)

Hence prove that V ≤ 144 for every possible value of x, and state the value of x for which V = 144.

(3)
Show mark scheme
AnswerMarkNotes
Part (a)
base (16 − 2x) cm by (10 − 2x) cm, height x cm: V = x(16 − 2x)(10 − 2x)M1
= x(160 − 52x + 4x2) = 4x3 − 52x2 + 160xA1
Part (b)
0 < x < 5B1
Part (c)
4x3 − 52x2 + 160x − 144 = 0, and dividing by 4 gives x3 − 13x2 + 40x − 36 = 0B1
x = 2: 8 − 52 + 80 − 36 = 0, so (x − 2) is a factorB1
Part (d)
divides by (x − 2)M1
quadratic factor x2 − 11x + 18A1
(x − 2)2(x − 9)A1
Part (e)
144 − V = −4(x3 − 13x2 + 40x − 36) = 4(x − 2)2(9 − x)M1
(x − 2)2 ≥ 0 and 9 − x > 0 for 0 < x < 5, so 144 − V ≥ 0, i.e. V ≤ 144A1
equality only when (x − 2)2 = 0, i.e. x = 2A1

Common error: Including x = 9 as a value that gives a volume of 144 cm³. The squares must fit on the 10 cm side, so x &lt; 5 and x = 9 is impossible for the box.

28IALM-P2-1-FB-14 P2 · ASHard12 marks

f(x) = 6x3 + px2 + qx − 8, where p and q are constants.
Figure 1 shows an incomplete grid used to divide f(x) by (2x + 1). The quotient is the sum of the three column headings, and when f(x) is divided by (2x + 1) the remainder is the constant R.

×3x²??2x6x³−10x²?+1??+2Each cell = (row heading) × (column heading).The quotient is the sum of the column headings.
(a)

Use Figure 1 to find the quotient.

(3)
(b)

Complete the grid, and hence find the values of p, q and R.

(3)
(c)

Use the remainder theorem to verify your value of R.

(2)
(d)

Hence factorise f(x) + 10 completely.

(2)
(e)

Find the set of values of x for which f(x) > −10.

(2)
Show mark scheme
AnswerMarkNotes
Part (a)
second heading: −10x2 ÷ 2x = −5xB1
third heading: +2 ÷ (+1) = +2B1
quotient 3x2 − 5x + 2B1
Part (b)
missing cells: 4x in the 2x row; 3x2 and −5x in the +1 rowM1
p = −10 + 3 = −7 and q = 4 − 5 = −1A1
constant term: 2 + R = −8, so R = −10A1
Part (c)
f(−½) = 6(−⅛) − 7(¼) − (−½) − 8M1
= −3/4 − 7/4 + 2/4 − 32/4 = −10 ✓A1
Part (d)
f(x) + 10 = (2x + 1)(3x2 − 5x + 2)M1
= (2x + 1)(3x − 2)(x − 1)A1
Part (e)
need (2x + 1)(3x − 2)(x − 1) > 0, with critical values −½, ⅔ and 1M1
−½ < x < ⅔ or x > 1A1

Exam tip: In a division grid, each missing heading comes from one known cell: divide that cell by its row heading. The remainder is whatever is needed to make the constant term match.