# How do you simplify (-8+9i)(6+9i)?

Oct 21, 2016

$- 129 - 18 i$

#### Explanation:

FOIL out the binomials:

$\left(- 8 + 9 i\right) \left(6 + 9 i\right) = - 48 - 72 i + 54 i + 81 {i}^{2}$

Combining the $i$ terms:

$= - 48 - 18 i + 81 {i}^{2}$

Recall that since $i = \sqrt{- 1}$ so ${i}^{2} = - 1$:

$= - 48 - 18 i + 81 \left(- 1\right)$

$= - 48 - 81 - 18 i$

$= - 129 - 18 i$