# How do you simplify -2i(-4i)?

$- 8$
$- 2 i \left(- 4 i\right) = - 2 i \times - 4 i = 8 {i}^{2}$
now ${i}^{2} = {\left(\sqrt{- 1}\right)}^{2} = - 1$
$\Rightarrow - 2 i \left(- 4 i\right) = 8 {i}^{2} = 8 \times \left(- 1\right) = - 8$