Question

Square of the complex number (i - 2)?

Answer 1

$(i-2)^{2} = i^{2} -4i+4 \\ i= \sqrt{-1} \\ i^{2} =-1 \\ i^{2} -4i+4=-1-4i+4=-4i+3\\ answer: 3-4i$

Answer 2

$(i-2)^2=\\--------------------\\use:(a-b)^2=a^2-2ab+b^2\\--------------------\\=i^2-2\times i\times2+2^2=-1-4i+4=3-4i\\\\\\\\i=\sqrt{-1}\Rightarrow i^2=-1$