Question
Answer
$$(9+7i)\cdot(2-8i)=-56i^2-58i+18$$
Explanation
Tap the blue circles to see an explanation.
| $$ \begin{aligned}(9+7i)\cdot(2-8i)& \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle1}{\textcircled {1}} } }}}18-72i+14i-56i^2 \xlongequal{ } \\[1 em] & \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle2}{\textcircled {2}} } }}}-56i^2-58i+18\end{aligned} $$ | |
| ① | Multiply each term of $ \left( \color{blue}{9+7i}\right) $ by each term in $ \left( 2-8i\right) $. $$ \left( \color{blue}{9+7i}\right) \cdot \left( 2-8i\right) = 18-72i+14i-56i^2 $$ |
| ② | Combine like terms: $$ 18 \color{blue}{-72i} + \color{blue}{14i} -56i^2 = -56i^2 \color{blue}{-58i} +18 $$ |
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