2022 EJC Promo Q4

2022 EJC Promo Q4

8 marks
  1. Sketch, on the same axes, the graphs of \(y = \ln(4x)\) and \(y = \left|x^3 - 2\right|\) for \(x > 0\).
    Hence, solve the inequality \(\left|x^3 - 2\right| > \ln(4x)\).[4]
  2. Using your answer in part (a), find the solution of \(\left|\frac{1 - 2x^3}{x^3}\right| + \ln x > \ln 4\) for \(x > 0\).[3]
  3. State the solution of the inequality \(\left|x^3 - 2\right| < -x\) for \(x > 0\).[1]

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Answer:(a) \(0 < x < 0.897\) or \(x>1.57\) (b) \(x>1.11\) or \(0 < x < 0.639\) (c) Since \(\left| {{x}^{3}}-2 \right|\) is non-negative for all values of \(x\) and \(-x\) is negative for \(x>0\), there is no solution.

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