2023 TMJC Promo Q2

2023 TMJC Promo Q2

5 marks
Promo

Functions \(\mathrm{f}\) and \(\mathrm{g}\) are defined by

\(\mathrm{f}:x\mapsto \frac{2x+7}{x-2}\), \(x\in \mathbb{R},\)\(x\ne 2\),

\(\mathrm{g}:x\mapsto {{\left( x-1 \right)}^{2}}-2\), \(x\in \mathbb{R},\)\(0 < x < 3\)

  1. Show that the composite function \(\mathrm{fg}\) exists.[2]
  2. Define \(\mathrm{fg}\) in a similar form and find its range.[3]

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Answer:(i) \(R_{\mathrm g}=[-2,2)\subset D_{\mathrm f}\), so \(\mathrm{fg}\) exists (ii) \(\mathrm{fg}:x\mapsto\dfrac{2x^2-4x+5}{x^2-2x-3}\), \(0<x<3\), with range \(\left(-\infty,-\dfrac34\right]\)

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