Answer
$3-15i$
Work Step by Step
We first use the FOIL method to simplify the expression. Then, knowing that $i=\sqrt{-1}$, we can substitute $-1$ for $i^{2}$ to obtain:
$(6+9i)(-1-i)$
=$6(-1-i)+9i(-1-i)$
=$-6-6i-9i-9i^{2}$
=$-6-15i-9i^{2}$
=$-6-15i-9(-1)$
=$-6+9-15i$
=$3-15i$
