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