2014 HCI P1 Q3 [Modified]

2014 HCI P1 Q3 [Modified]

Prelims
  1. Given that imaginary unit \(\mathbf{i}\) is one of the roots of the equation \({{z}^{3}}-2{{z}^{2}}+az+1+3\mathbf{i}=0\), find the complex number \({a}\) and the other roots.
  2. The root that has the largest modulus in (a) is denoted as \({w}\) and represented by the point \({A}\). The points \({B, C}\) and \({D}\) represent the complex numbers \({{w}^{*}}\), \(\mathbf{i}w\) and \({{\mathbf{i}}^{2}}w\) respectively. On the same diagram, plot the points \({A, B, C}\) and \({D}\) and state each transformation that maps the point \({A}\) onto the point \({B, C}\) and \({D}\) respectively and state the angle \({OAC}\).

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Answer:(a) \({a = -2+3\mathbf{i}\,,\; z = -1 \text{ or}\hspace{0.5em} 3-\mathrm{i}}\)

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