2015 NYJC P2 Q2

2015 NYJC P2 Q2

10 marks
Prelims
  1. The function \(\mathrm{f}\) is defined by
    \(\mathrm{f}:x\mapsto \frac{2x-1}{2x-2},\quad x < 1\).
    Define \({{\mathrm{f}}^{-1}}\) in a similar form. Hence or otherwise find \({{\mathrm{f}}^{2}}(x)\) and state the value of \({{\mathrm{f}}^{1965}}(0.5)\).[5]
  2. The function \(\mathrm{g}\) is defined by
    \(\mathrm{g}:x\mapsto \sqrt{4+2x},\quad x\in \mathbb{R},\ \ 0\le x < 16.\)
    1. Sketch the graph of \(y=\mathrm{g}(x)\). Your sketch should indicate the coordinates of the end-points.[2]
    2. On the same diagram of part (i), sketch the graph of \(y={{\mathrm{g}}^{-1}}(x)\), showing the relationship between \(\mathrm{g}\) and \({{\mathrm{g}}^{-1}}\).[2]
    3. Find the values of \(x\) satisfying the equation \({{\mathrm{g}}^{-1}}\mathrm{g}(x)=\mathrm{g}{{\mathrm{g}}^{-1}}(x)\).[1]

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Answer:(a) \(\mathrm f^{-1}(x)=\dfrac{2x-1}{2x-2}\), \(x<1\); \(\mathrm f^2(x)=x\), and \(\mathrm f^{1965}(0.5)=0\) (b)(i) Closed endpoint \((0,2)\), open endpoint \((16,6)\) (b)(ii) \(\mathrm g^{-1}(x)=\dfrac{x^2-4}{2}\), \(2\leq x<6\), reflected in \(y=x\) (b)(iii) \(2\leq x<6\)

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