Question

Express (1-2i) second power in the form a+bi

Answer 1

$\bf (1-2i)^2\implies (1-2i)(1-2i)\implies 1-2i-2i+(2i)^2 \\\\\\ 1-4i+(2^2i^2)\implies \stackrel{\textit{recall }i^2=-1}{1-4i+(4\cdot -1)}\implies 1-4i-4\implies \boxed{-3-4i}$