## Differential Equations and Linear Algebra (4th Edition)

We know that $i^2=-1$ $z_1z_2=(-1+3i)(2-i)=-2+i+6i+3=1+7i$ $z_1/z_2=\frac{-1+3i}{2-i}=\frac{(-1+3i)(2+i)}{(2-i)(2+i)}=\frac{-2-i+6i-3}{4+1}=\frac{-5+5i}{5}=-1+i$