AQA FP2 2012 June — Question 4

Exam BoardAQA
ModuleFP2 (Further Pure Mathematics 2)
Year2012
SessionJune
TopicRoots of polynomials

4 The cubic equation $$z ^ { 3 } + p z + q = 0$$ has roots \(\alpha , \beta\) and \(\gamma\).
    1. Write down the value of \(\alpha + \beta + \gamma\).
    2. Express \(\alpha \beta \gamma\) in terms of \(q\).
  1. Show that $$\alpha ^ { 3 } + \beta ^ { 3 } + \gamma ^ { 3 } = 3 \alpha \beta \gamma$$
  2. Given that \(\alpha = 4 + 7 \mathrm { i }\) and that \(p\) and \(q\) are real, find the values of:
    1. \(\beta\) and \(\gamma\);
    2. \(p\) and \(q\).
  3. Find a cubic equation with integer coefficients which has roots \(\frac { 1 } { \alpha } , \frac { 1 } { \beta }\) and \(\frac { 1 } { \gamma }\).