2023 RVHS Promo Q3

2023 RVHS Promo Q3

7 marks
Promo

The function \(\mathrm{f}\) is given by \(\mathrm{f}:x\mapsto \frac{1}{x-2}+5\), \(x>2\).

  1. Explain why \({{\mathrm{f}}^{-1}}\) exists.[1]
  2. Find \({{\mathrm{f}}^{-1}}\) in similar form.[3]
  3. Find \(\mathrm{ff}\) in a similar form and the exact range of \(\mathrm{ff}\).[3]

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Answer:(i) \(\mathrm f^{-1}\) exists because \(\mathrm f\) is one-to-one (ii) \(\mathrm f^{-1}:x\mapsto\dfrac1{x-5}+2\), \(x>5\) (iii) \(\mathrm{ff}:x\mapsto\dfrac{x-2}{3x-5}+5\), \(x>2\), with \(R_{\mathrm{ff}}=\left(5,\dfrac{16}{3}\right)\)

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