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