Question
Answer
$$(2+4i)\cdot(-7-4i)=-16i^2-36i-14$$
Explanation
Tap the blue circles to see an explanation.
| $$ \begin{aligned}(2+4i)\cdot(-7-4i)& \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle1}{\textcircled {1}} } }}}-14-8i-28i-16i^2 \xlongequal{ } \\[1 em] & \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle2}{\textcircled {2}} } }}}-16i^2-36i-14\end{aligned} $$ | |
| ① | Multiply each term of $ \left( \color{blue}{2+4i}\right) $ by each term in $ \left( -7-4i\right) $. $$ \left( \color{blue}{2+4i}\right) \cdot \left( -7-4i\right) = -14-8i-28i-16i^2 $$ |
| ② | Combine like terms: $$ -14 \color{blue}{-8i} \color{blue}{-28i} -16i^2 = -16i^2 \color{blue}{-36i} -14 $$ |
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