Answer
$$(5-i)\cdot(3+6i)=-6i^2+27i+15$$
Explanation
Tap the blue circles to see an explanation.
| $$ \begin{aligned}(5-i)\cdot(3+6i)& \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle1}{\textcircled {1}} } }}}15+30i-3i-6i^2 \xlongequal{ } \\[1 em] & \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle2}{\textcircled {2}} } }}}-6i^2+27i+15\end{aligned} $$ | |
| ① | Multiply each term of $ \left( \color{blue}{5-i}\right) $ by each term in $ \left( 3+6i\right) $. $$ \left( \color{blue}{5-i}\right) \cdot \left( 3+6i\right) = 15+30i-3i-6i^2 $$ |
| ② | Combine like terms: $$ 15+ \color{blue}{30i} \color{blue}{-3i} -6i^2 = -6i^2+ \color{blue}{27i} +15 $$ |
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