AQA FP1 — Question 5

Exam BoardAQA
ModuleFP1 (Further Pure Mathematics 1)
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Mark schemeDownload PDF ↗
TopicComplex Numbers Arithmetic

5
    1. Calculate \(( 2 + \mathrm { i } \sqrt { 5 } ) ( \sqrt { 5 } - \mathrm { i } )\).
    2. Hence verify that \(\sqrt { 5 } - \mathrm { i }\) is a root of the equation $$( 2 + \mathrm { i } \sqrt { 5 } ) z = 3 z ^ { * }$$ where \(z ^ { * }\) is the conjugate of \(z\).
  1. The quadratic equation $$x ^ { 2 } + p x + q = 0$$ in which the coefficients \(p\) and \(q\) are real, has a complex root \(\sqrt { 5 } - \mathrm { i }\).
    1. Write down the other root of the equation.
    2. Find the sum and product of the two roots of the equation.
    3. Hence state the values of \(p\) and \(q\).

5 (a) (i) Calculate $( 2 + \mathrm { i } \sqrt { 5 } ) ( \sqrt { 5 } - \mathrm { i } )$.\\
(ii) Hence verify that $\sqrt { 5 } - \mathrm { i }$ is a root of the equation

$$( 2 + \mathrm { i } \sqrt { 5 } ) z = 3 z ^ { * }$$

where $z ^ { * }$ is the conjugate of $z$.\\
(b) The quadratic equation

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

in which the coefficients $p$ and $q$ are real, has a complex root $\sqrt { 5 } - \mathrm { i }$.\\
(i) Write down the other root of the equation.\\
(ii) Find the sum and product of the two roots of the equation.\\
(iii) Hence state the values of $p$ and $q$.

\hfill \mbox{\textit{AQA FP1  Q5}}