2025 MI P2 Q5

2025 MI P2 Q5

10 marks

The function \(\mathrm{g}\) is given by \(\mathrm{g} : x \mapsto \frac{x-3}{x-1}\), for \(x \in \mathbb{R}\), \(x \neq 1\).

  1. Sketch the graph of \(y = \mathrm{g}(x)\), stating clearly the coordinates of any points of intersection with the axes and the equation of any asymptotes.[3]
  2. Explain if \(\mathrm{g}^{-1}\) exists.[1]
  3. Find \(\mathrm{g}^{-1}(x)\) and state the domain of \(\mathrm{g}^{-1}\).[3]

A function \(\mathrm{f}\) is said to be self-inverse if \(\mathrm{f}(x) = \mathrm{f}^{-1}(x)\) for all \(x \in \mathbb{R}\) in the domain of \(\mathrm{f}\).

  1. Show that \(\mathrm{g}\) is self-inverse.[1]
  2. Without the use of a calculator, solve the equation \(\mathrm{g}^2(x) = -\mathrm{g}^{-1}(x)\).[2]

Solution:

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Answer:(i) Intercepts \((0,3)\), \((3,0)\); asymptotes \(x=1\), \(y=1\); sketch shown. (ii) Inverse exists. (iii) \(\mathrm{g}^{-1}(x)=\frac{x-3}{x-1}\), \(x\ne1\). (iv) Self-inverse, as shown. (v) \(x=\pm\sqrt3\).

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