Question

How do you multiply `(2-4i)(3+5i)`?

Answer 1

`(2-4i)(3+5i) =26-2i`

Explanation:

`(2-4i)(3+5i) =(2)(3)+(2)(5i)+(-4i)(3)+(-4i)(5i)`
`:. (2-4i)(3+5i) =6+10i-12i-20i^2`
`:. (2-4i)(3+5i) =6-2i-20i^2`

Now `i^2=-1`, so
`:. (2-4i)(3+5i) =6-2i+20`
`:. (2-4i)(3+5i) =6-2i+20`
`:. (2-4i)(3+5i) =26-2i`