Question
Answer
$$(1+5i)\cdot(-3-i)=-5i^2-16i-3$$
Explanation
Tap the blue circles to see an explanation.
| $$ \begin{aligned}(1+5i)\cdot(-3-i)& \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle1}{\textcircled {1}} } }}}-3-i-15i-5i^2 \xlongequal{ } \\[1 em] & \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle2}{\textcircled {2}} } }}}-5i^2-16i-3\end{aligned} $$ | |
| ① | Multiply each term of $ \left( \color{blue}{1+5i}\right) $ by each term in $ \left( -3-i\right) $. $$ \left( \color{blue}{1+5i}\right) \cdot \left( -3-i\right) = -3-i-15i-5i^2 $$ |
| ② | Combine like terms: $$ -3 \color{blue}{-i} \color{blue}{-15i} -5i^2 = -5i^2 \color{blue}{-16i} -3 $$ |
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