Question
Answer
$$(9-3i)\cdot(6+i)=-3i^2-9i+54$$
Explanation
Tap the blue circles to see an explanation.
| $$ \begin{aligned}(9-3i)\cdot(6+i)& \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle1}{\textcircled {1}} } }}}54+9i-18i-3i^2 \xlongequal{ } \\[1 em] & \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle2}{\textcircled {2}} } }}}-3i^2-9i+54\end{aligned} $$ | |
| ① | Multiply each term of $ \left( \color{blue}{9-3i}\right) $ by each term in $ \left( 6+i\right) $. $$ \left( \color{blue}{9-3i}\right) \cdot \left( 6+i\right) = 54+9i-18i-3i^2 $$ |
| ② | Combine like terms: $$ 54+ \color{blue}{9i} \color{blue}{-18i} -3i^2 = -3i^2 \color{blue}{-9i} +54 $$ |
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