2023 CJC Promo Q7

2023 CJC Promo Q7

10 marks
Promo
  1. The curve \(y=\mathrm{f}(x)\) cuts the axes at \(\left( 1,0 \right)\) and \(\left( 0,-2 \right)\). It is given that \({{\mathrm{f}}^{-1}}\) exists. State, if it is possible to do so, the coordinates of the points where the following curves cut the axes.
    1. \(y={{\mathrm{f}}^{-1}}(x)\)[1]
    2. \(y=\mathrm{f}\left( \frac{1}{2}x \right)\)[1]
    3. \(y=\mathrm{f}\left( \frac{1}{2}x+1 \right)\)[1]
  2. Two functions \(\mathrm{g}\) and \(\mathrm{h}\) are defined as follows:
    \(\mathrm{g}:x\mapsto \sqrt{x+2}\),\(x\in \mathbb{R}\), \(x\ge -2\) ,
    \(\mathrm{h}:x\mapsto {{x}^{2}}-4x+5\), \(x\in \mathbb{R}\), \(x\ge 0\).
    1. Show that \(\mathrm{gh}\) exists and find the exact range of \(\mathrm{gh}\).[4]
    2. Use a non-calculator method to solve \(\mathrm{gh}\left( x \right)=2x\).[3]

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Answer:(a)(i) \((0,1)\) and \((-2,0)\) (a)(ii) \((2,0)\) and \((0,-2)\) (a)(iii) \((0,0)\) only (b)(i) \(gh\) exists and \(R_{gh}=[\sqrt3,\infty)\) (b)(ii) \(x=1\)

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