2023 SAJC Promo Q8

2023 SAJC Promo Q8

7 marks
Promo

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

\(\mathrm{f}:x\mapsto \frac{-x-3}{x+1}\), for \(\mathrm{ }x\in \mathbb{R}\), \(x\ne k\)

  1. State the value of \(k\) and explain why this value has to be excluded from the domain of \(\mathrm{f}\).[2]
  2. Find \({{\mathrm{f}}^{-1}}\). Hence find \({{\mathrm{f}}^{2}}\left( x \right)\).[3]

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

\(\mathrm{g}:x\mapsto \sqrt{x+1}\), \(x\in \mathbb{R}\), \(x>-1\)

  1. Find the range of \(\mathrm{fg}\).[2]

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Answer:(i) \(k=-1\) (ii) \({{\mathrm{f}}^{2}}\left( x \right)=x\) (iii) \({{\mathrm{R}}_{\mathrm{fg}}}=\left( -3,-1 \right)\)

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