Tap the blue circles to see an explanation.
$$ \begin{aligned}(-9-6i)\cdot(11-7i)& \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle1}{\textcircled {1}} } }}}-99+63i-66i+42i^2 \xlongequal{ } \\[1 em] & \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle2}{\textcircled {2}} } }}}42i^2-3i-99\end{aligned} $$ | |
① | Multiply each term of $ \left( \color{blue}{-9-6i}\right) $ by each term in $ \left( 11-7i\right) $. $$ \left( \color{blue}{-9-6i}\right) \cdot \left( 11-7i\right) = -99+63i-66i+42i^2 $$ |
② | Combine like terms: $$ -99+ \color{blue}{63i} \color{blue}{-66i} +42i^2 = 42i^2 \color{blue}{-3i} -99 $$ |