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4MA1/2HR Jun 2025, Question 19: Composite Functions

Pearson Edexcel International GCSE Mathematics A 4MA1 · Paper 2HR (Higher) · Calculator · 3 marks

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The question, in short

Given f(x) = 3x − 4 for x > 2 and g(x) = x/(2x + 1), state an excluded x value for g and find the composite gf(x) in simplest form.

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Part (a) · 1 mark

State which value of x must be excluded from any domain of g.

  1. 1The denominator cannot be 0
  2. 22x + 1 = 0
  3. 3x = −1/2

Answer−1/2

Part (b) · 2 marks

Find gf(x) and give the result in its simplest form.

  1. 1gf(x) = g(3x − 4)
  2. 2= (3x − 4)/(2(3x − 4) + 1)
  3. 3= (3x − 4)/(6x − 8 + 1)
  4. 4= (3x − 4)/(6x − 7)

Answer(3x − 4)/(6x − 7)

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