Answer only one of the following two alternatives. OR The functions f, g and h are defined, for x ∈ R, by f(x) = x² + 1, g(x) = 2x - 5, h(x) = 2ˣ.
- (i)Write down the range of f.[1]
- (ii)Find the value of gf(3).[2]
- (iii)Solve the equation fg(x) = g⁻¹(15).[5]
- (iv)On the same axes, sketch the graph of y = h(x) and the graph of the inverse function y = h⁻¹(x), indicating clearly which graph represents h and which graph represents h⁻¹.[2]
This question uses a diagram from the original paper, which isn't shown here. Open the full paper from the past papers archive to see it.
Mark scheme
Marking points from the official mark scheme (May/June 2010). The mark or mark type is shown in brackets.
- B1 for (f) ≥ 1
- M1 for gf(3)=g(10) or gf(x) = 2(x²+1)-5
- A1 for 15
- B1 for g⁻¹(15) = 10
- M1 for Finds fg(x)
- A1 for (2x-5)² + 1 or 4x² - 20x + 26
- M1 for Solves (2x-5)²+1=10 or 4x² −20x+16=0
- A1 for 1 and 4
- B1 for complete, labelled exponential curve
- B1 for complete logarithmic curve not cutting exponential curve
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