Printable · GCSE Higher · ages 14-16

Functions, inverse and composite functions worksheet — GCSE Higher

Fifteen questions on "functions, inverse and composite functions" — DfE statement A7. Print it, or print three versions so neighbours cannot copy by letter; the key gives the letter for each version.

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Functions, inverse and composite functions worksheet — GCSE Higher

Maths · GCSE Higher · A7 · Functions, inverse and composite functions · 15 questions

MathsUKwww.geekhero.co.uk

1.f(x) = x + 2 and g(x) = x². Work out the value of x for which fg(x) = gf(x).
y = x + 2
(a)1.5
(b)0
(c)−0.5
(d)no solution
2.A rule turns each input x into an output y. The inputs are x = 1, 2, 3, 4 and the matching outputs are y = −5, −3, −1 and one missing value. Work out the missing value of y.
(a)0
(b)8
(c)3
(d)1
3.f(x) = 3x − 2. Find f⁻¹(x).
y = 3x − 2
(a)(x − 2)/3
(b)(x + 2)/3
(c)3x + 2
(d)x/3 + 2
4.f(x) = 2x + 1. Work out the value of x for which f⁻¹(x) = 5.
y = 2x + 1
(a)6
(b)9
(c)2
(d)11
5.A rule turns each input x into an output y. The inputs are x = −1, 0, 1, 2 and the matching outputs are y = 5, 3, 1, −1. Work out the rule.
(a)y = −2x + 3
(b)y = 2x + 3
(c)y = −2x − 3
(d)y = −x + 4
6.A plumber charges a call-out fee of £30 plus £25 per hour worked. Work out the total charge for a job that takes 3 hours.
(a)£165
(b)£105
(c)£75
(d)£90
7.A rule turns each input into an output. An input of 0 gives an output of −1, an input of 1 gives an output of 1, and an input of 2 gives an output of 3. Work out the rule, writing the input as x and the output as y.
(a)y = x − 1
(b)y = 2x − 1
(c)y = 3x − 1
(d)y = 2x + 1
8.y = 5 − 2x. Work out the value of x when y = 11.
(a)8
(b)3
(c)6
(d)−3
9.f(x) = x² − 1 and g(x) = 3x. Work out fg(4).
y = x² − 1
(a)36
(b)143
(c)11
(d)45
10.Ben is asked to find the inverse of f(x) = 4 − 3x. He writes f⁻¹(x) = (4 − x)/3. Which statement about Ben's answer is correct?
(a)Wrong: sign kept, giving f⁻¹(x) = (−4 − x)/3
(b)Correct, but only because f is its own inverse
(c)Correct: 3y = 4 − x gives f⁻¹(x) = (4 − x)/3
(d)Wrong: correct inverse is f⁻¹(x) = (x − 4)/3
11.f(x) = (x + 1)/2. Find f⁻¹(x).
(a)2x − 1
(b)(x − 1)/2
(c)x/2 − 1
(d)2x + 1
12.A rule multiplies the input by a fixed number and then adds a fixed number. An input of 1 gives an output of 5, and an input of 3 gives an output of 11. Work out the rule, writing the input as x and the output as y.
(a)y = 3x − 2
(b)y = x + 4
(c)y = 3x + 2
(d)y = 2x + 3
13.A number machine multiplies its input by 3 and then adds 7. The output is 1. Work out the input.
(a)2
(b)−18
(c)−6
(d)−2
14.f(x) = x + 3 and g(x) = 2x. Work out fg(x).
y = x + 3
(a)2x² + 6x
(b)2x + 3
(c)3x + 3
(d)2x + 6
15.f(x) = 2x² + 1 and g(x) = x − 1. Work out fg(x), giving your answer in expanded form.
y = 2x² + 1
(a)2x² − 4x + 2
(b)2x² − 1
(c)2x²
(d)2x² − 4x + 3

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