комплексные-числа - Уравнение на множестве комплексных чисел

$%z^{4} - 2z^{2} +4 = 0 \Leftrightarrow \left[\begin{aligned} z^2=1-\sqrt3i\\ z^2=1+\sqrt3i \end{aligned}\right.\\\Leftrightarrow \left[\begin{aligned} z=\pm \sqrt{1-\sqrt3i}\\ z=\pm \sqrt{1+\sqrt3i} \end{aligned}\right.\\\Leftrightarrow \left[\begin{aligned} z=\pm (\sqrt{\frac{3}{2}}-\frac{i}{\sqrt{2}})\\ z=\pm (\sqrt{\frac{3}{2}}+\frac{i}{\sqrt{2}})\end{aligned}\right.\\$%