Answer
$$(-3+i)\cdot(3+8i)=8i^2-21i-9$$
Explanation
Tap the blue circles to see an explanation.
| $$ \begin{aligned}(-3+i)\cdot(3+8i)& \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle1}{\textcircled {1}} } }}}-9-24i+3i+8i^2 \xlongequal{ } \\[1 em] & \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle2}{\textcircled {2}} } }}}8i^2-21i-9\end{aligned} $$ | |
| ① | Multiply each term of $ \left( \color{blue}{-3+i}\right) $ by each term in $ \left( 3+8i\right) $. $$ \left( \color{blue}{-3+i}\right) \cdot \left( 3+8i\right) = -9-24i+3i+8i^2 $$ |
| ② | Combine like terms: $$ -9 \color{blue}{-24i} + \color{blue}{3i} +8i^2 = 8i^2 \color{blue}{-21i} -9 $$ |
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