Question
Answer
$$(9-9i)\cdot(-8-10i)=90i^2-18i-72$$
Explanation
Tap the blue circles to see an explanation.
| $$ \begin{aligned}(9-9i)\cdot(-8-10i)& \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle1}{\textcircled {1}} } }}}-72-90i+72i+90i^2 \xlongequal{ } \\[1 em] & \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle2}{\textcircled {2}} } }}}90i^2-18i-72\end{aligned} $$ | |
| ① | Multiply each term of $ \left( \color{blue}{9-9i}\right) $ by each term in $ \left( -8-10i\right) $. $$ \left( \color{blue}{9-9i}\right) \cdot \left( -8-10i\right) = -72-90i+72i+90i^2 $$ |
| ② | Combine like terms: $$ -72 \color{blue}{-90i} + \color{blue}{72i} +90i^2 = 90i^2 \color{blue}{-18i} -72 $$ |
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