2019 DHS Promo Q8

2019 DHS Promo Q8

9 marks
Promo

The function \(\mathrm{f}\) is defined by

\(\mathrm{f}:x\mapsto \frac{2x}{x-2}\), for \(x\in \mathbb{R},x\ne 2\).

  1. Find \({{\mathrm{f}}^{-1}}\left( x \right)\), stating the domain of \({{\mathrm{f}}^{-1}}\).[2]
  2. Solve the equation \(\mathrm{f}\left( x \right)={{\mathrm{f}}^{-1}}\left( x \right)\).[1]

The function \(\mathrm{g}\) is defined as follows.

\(\mathrm{g}:x\mapsto \frac{2}{x-3}\), for \(x\in \mathbb{R},x\ne 3,x\ne 4\).

  1. Find \(\mathrm{fg}\left( x \right)\).[1]
  2. Solve the inequality \(\mathrm{fg}\left( x \right) < x\) for all \(x\) in the domain of \(\mathrm{fg}\).[3]
  3. Find the range of \(\mathrm{fg}\).[2]

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Answer:\(2 - \sqrt{2} < x < 2 + \sqrt{2}\), \(x \neq 3\)

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