Target Mathematics

3.2: Exponential function inverse, sketch and composite

0606/22/F/M/23 — Question 8 · 13 marks

The function ff is defined for x0x \geqslant 0 by f(x)=52exf(x) = 5 - 2\mathrm{e}^{-x}.
(a)(i)
Find the domain of f1f^{-1}.
[2]
(a)(ii)
Solve ff1(x)=5x4ff^{-1}(x) = \sqrt{5x - 4}.
[3]
(a)(iii)
On the axes, sketch the graph of y=f(x)y = f(x) and hence sketch the graph of y=f1(x)y = f^{-1}(x). Show clearly the positions of any points where your graphs meet the coordinate axes and the positions of any asymptotes.
[4]
(b)
The function gg is defined for 0x0.20 \leqslant x \leqslant 0.2 by g(x)=31xg(x) = \dfrac{3}{1 - x}.
Find and simplify an expression for f1g(x)f^{-1}g(x).
[4]