2014 JJC Promo Q8

2014 JJC Promo Q8

10 marks
Promo

The function \(\mathrm{f}\) is defined by \(\mathrm{f}:x\mapsto \frac{x-1}{x}\), \(x\in \mathbb{R}\), \(x\ne 0\) and \(x\ne 1\).

  1. Define \({{\mathrm{f}}^{-1}}\).[3]
  2. Show that the composite function \({{\mathrm{f}}^{2}}\) exists and that \({{\mathrm{f}}^{2}}\left( x \right)={{\mathrm{f}}^{-1}}\left( x \right)\).[3]
  3. State \({{\mathrm{f}}^{3}}\left( x \right)\).[1]
  4. Given that \({{\mathrm{f}}^{2014}}\mathrm{g}\left( x \right)=1-{{\mathrm{e}}^{-x}}\) for \(x>0\), find \(\mathrm{g}\left( x \right)\).[3]

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Answer:(i) \({\mathrm{f}^{-1}:x \mapsto \frac{1}{1-x}\,,\; x \in \mathbb{R},\; x \neq 0 \text{ and}\hspace{0.5em} x \neq 1}\) (iii) \({\mathrm{f}^3(x)=x}\) (iv) \({\mathrm{g}(x) = \mathrm{e}^x}\)

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