Quadratic Functions, Equations and Inequalities - Nature of Roots of Quadratic Equations

Quadratic Functions, Equations and Inequalities - Nature of Roots of Quadratic Equations

Secondary 4
11 marks

It is given that \(f(x)=3x^3+2x^2+16\). The remainder when \(f(x)\) is divided by \(x-3a\), where \(a\) is a constant, is the same as the remainder when it is divided by \(3x+2\).

  1. Find the possible values of \(a\).[3]
  2. Show, with clear working, that \(x=-2\) is a solution of \(f(x)=0\).[1]
  3. Explain why \(f(x)=0\) has only one real root.[5]
  4. Hence use your answers to parts (b) and (c) to solve the equation[2]
    \[16y^3+2y-3=0.\]

Solution:

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Answer:(a) \(a=0\) or \(a=-\frac{2}{9}\) (b) \(x=-2\) (c) Only one real root (d) \(y=\frac{1}{2}\)

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