2021 SAJC Promo Q6

2021 SAJC Promo Q6

11 marks
Promo
  1. The graph of \(y=\mathrm{h}\left( x \right)\), where \(\mathrm{h}\left( x \right)={{\mathrm{e}}^{3x}}\), was transformed to a new graph with equation \(y=\mathrm{g}\left( x \right)\).
    1. Given that \(\mathrm{g}\left( x \right)=\frac{1}{\mathrm{h}'\left( x \right)}\), express \(\mathrm{g}\left( x \right)\) in the form of \(k{{\mathrm{e}}^{mx}}\) where \(k\) and \(m\) are exact real constants.[1]
    2. Describe a sequence of two transformations which would transform the graph of \(y=\mathrm{h}\left( x \right)\) to the graph of \(y=\mathrm{g}\left( x \right)\).[2]
  2. The diagram below shows the curve \(y=\mathrm{f}\left( x \right)\). The curve has a minimum point \(\left( -3,-4 \right)\) and passes through the origin. The lines \(x=3\) and \(y=-2\) are the vertical and horizontal asymptotes to the curve respectively.
    List item image
    1. Sketch, including the coordinates of the point(s) of intersections with the axes, turning point(s) and equation(s), if any, the following:
      (a) \(\quad y=-\frac{1}{2}\mathrm{f}\left( x-3 \right)\).[4]
      (b) \(\quad y=\frac{1}{\mathrm{f}\left( x \right)}\).[3]
    2. State the coordinates of the point(s) where the curve \(y=\mathrm{f}'\left( x \right)\) cuts the axes.[1]

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Answer:(i) \(\text{g}\hspace{0.1em}\left( x \right)=\frac{1}{3}{{\text{e}}^{-3x}}\) (ii) Reflection about the \(y\)-axis, A scaling parallel to the \(y\)-axis with a scale factor of \(\frac{1}{3}\).

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