2026 ASRJC P1 Q9

2026 ASRJC P1 Q9

Junior College 2
9 marks

The function \(\mathrm{f}\) is defined by \[\mathrm{f}:x\mapsto-4x^2-2x+2,\qquad x\in\mathbb{R},\quad -2\leq x<2.\]

  1. Sketch the graph of \(y=\mathrm{f}(x)\), stating clearly the coordinates of the axial intercepts and end points.[2]
  2. Explain why \(\mathrm{f}^{-1}\) does not exist.[1]
  3. The function \(\mathrm{g}\) is defined by \[\mathrm{g}:x\mapsto-4x^2-2x+2,\qquad x\in\mathbb{R},\quad -2\leq x<-\frac14.\]
    Find \(\mathrm{g}^{-1}\) in a similar form.[4]
  4. The functions \(\mathrm{h}\) and \(\mathrm{k}\) are defined by \[\mathrm{h}:x\mapsto-\ln(x+1),\qquad x\in\mathbb{R},\quad x>-1,\] \[\mathrm{k}:x\mapsto|4x^2+2x-2|,\qquad x\in\mathbb{R},\quad -1\leq x<0.\]
    Show that \(\mathrm{hk}\) exists and find the exact range of the composite function \(\mathrm{hk}\).[2]

Solution:

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Answer:(a) vertex \((-\frac14,\frac94)\); intercepts \((-1,0)\), \((\frac12,0)\), \((0,2)\); endpoints \((-2,-10)\) closed, \((2,-18)\) open (b) not one-to-one (c) \(\mathrm{g}^{-1}(x)=\frac{-1-\sqrt{9-4x}}4\), \(-10\leq x<\frac94\) (d) \(\operatorname{Ran}(\mathrm{hk})=[-\ln\frac{13}{4},0]\)

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