# How do you multiply -4i(3-5i)?

$- 4 i \left(3 - 5 i\right) = - 20 - 12 i$
$- 4 i \left(3 - 5 i\right) = \left(- 4 i\right) \times 3 - \left(- 4 i\right) \times \left(5 i\right) = - 12 i + 20 {i}^{2}$
It is assumed that $i$ is not a variable, but is a unit imaginary number and hence ${i}^{2} = - 1$ and hence
$- 4 i \left(3 - 5 i\right) = - 12 i + 20 {i}^{2} = - 12 i - 20$ or $- 20 - 12 i$