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