$i ^{2}=-1$ $\sqrt{-64}=\sqrt{64 i ^{2}}$ Let A=7-6i and B=2-2i $1=(A+B)\div(A+B)$ $(8i \div(A-B))\times1=(8i \div(A-B))\times((A+B)\div(A+B))$ The resulted formula after simplification will be in the form of:$(8i \times (A+B))/(A ^{2}-B ^{2})$ Just replace A and B with 7-6i and 2-2i, you'll get your answer. ;)