2025 ACJC P2 Q4

2025 ACJC P2 Q4

Junior College 2
9 marks

The function \(\mathrm{f}\) is defined by \(\mathrm{f} : x \mapsto \frac{1}{x^2 + 6x + 5}\), for \(x \ge -3\), \(x \neq -1\).

  1. Find \(\mathrm{f}^{-1}(x)\).[3]
  2. Find algebraically the range of \(\mathrm{f}\).[4]

The function \(\mathrm{g}\) is defined by \(\mathrm{g} : x \mapsto e^x\), for \(x \in \mathbb{R}\).

  1. Find the exact range of \(\mathrm{gf}\).[2]

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Answer:(a) \(\mathrm f^{-1}(x)=-3+\sqrt{4+\dfrac1x}\), with domain \(\left(-\infty,-\dfrac14\right]\cup(0,\infty)\) (b) \(R_{\mathrm f}=\left(-\infty,-\dfrac14\right]\cup(0,\infty)\) (c) \(R_{\mathrm{gf}}=(0,e^{-1/4}]\cup(1,\infty)\)

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