N2014 P1 Q5

N2014 P1 Q5

7 marks
Past Year National Exams
Free

It is given that \(z=1+2\mathrm{i}\).

  1. Without using a calculator, find the values of \({{z}^{2}}\) and \(\frac{1}{{{z}^{3}}}\) in cartesian form \(x+\mathrm{i}y\), showing your working.[4]
  2. The real numbers \(p\) and \(q\) are such that \(p{{z}^{2}}+\frac{q}{{{z}^{3}}}\) is real. Find, in terms of \(p\), the value of \(q\) and the value of \(p{{z}^{2}}+\frac{q}{{{z}^{3}}}\).[3]

Video Solution:

Default solution

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Answer:(i) \(z^2=-3+4\mathrm{i}\), \(\displaystyle\frac1{z^3}=-\frac{11}{125}+\frac{2}{125}\mathrm{i}\) (ii) \(q=-250p\), \(\displaystyle pz^2+\frac q{z^3}=19p\)

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