CAIE FP1 2018 November — Question 2

Exam BoardCAIE
ModuleFP1 (Further Pure Mathematics 1)
Year2018
SessionNovember
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Mark schemeDownload PDF ↗
TopicRoots of polynomials

2 The roots of the equation $$x ^ { 3 } + p x ^ { 2 } + q x + r = 0$$ are \(\alpha , 2 \alpha , 4 \alpha\), where \(p , q , r\) and \(\alpha\) are non-zero real constants.
  1. Show that $$2 p \alpha + q = 0$$
  2. Show that $$p ^ { 3 } r - q ^ { 3 } = 0$$

2 The roots of the equation

$$x ^ { 3 } + p x ^ { 2 } + q x + r = 0$$

are $\alpha , 2 \alpha , 4 \alpha$, where $p , q , r$ and $\alpha$ are non-zero real constants.\\
(i) Show that

$$2 p \alpha + q = 0$$

(ii) Show that

$$p ^ { 3 } r - q ^ { 3 } = 0$$

\hfill \mbox{\textit{CAIE FP1 2018 Q2}}