Question

How do u solve this problem

Answer 1

$\text{Use}\\(a+b)^2=a^2+2ab+b^2\\\\i=\sqrt{-1}\to i^2=-1$

$1)\\(8+7i)^2=8^2+2\cdot8\cdot7i+(7i)^2=64+112i+49i^2\\\\=64+112i-49=15+112i$

$3)\\(-1+6i)^2=(-1)^2+2\cdot(-1)\cdot6i+(6i)^2=1-12i+36i^2\\\\=1-12i-36=-35-12i$