Express (4-5i) (-5+8i) in the form a+ bi, where a and b are integers and i^2 = -1
You can expand like it is a polynomial and then use i^2 = -1.
We use FOIL to get (4−5i)(−5+8i)=−20+25i+32i−40i2. Now use i^2 = -1 to get the answer.
