Question
Answer
$$(-5+2i)\cdot(-1-8i)=-16i^2+38i+5$$
Explanation
Tap the blue circles to see an explanation.
| $$ \begin{aligned}(-5+2i)\cdot(-1-8i)& \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle1}{\textcircled {1}} } }}}5+40i-2i-16i^2 \xlongequal{ } \\[1 em] & \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle2}{\textcircled {2}} } }}}-16i^2+38i+5\end{aligned} $$ | |
| ① | Multiply each term of $ \left( \color{blue}{-5+2i}\right) $ by each term in $ \left( -1-8i\right) $. $$ \left( \color{blue}{-5+2i}\right) \cdot \left( -1-8i\right) = 5+40i-2i-16i^2 $$ |
| ② | Combine like terms: $$ 5+ \color{blue}{40i} \color{blue}{-2i} -16i^2 = -16i^2+ \color{blue}{38i} +5 $$ |
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