Question
Answer
$$(5-6i)\cdot(-3+r\cdot2i)=-12i^2r+10ir+18i-15$$
Explanation
Tap the blue circles to see an explanation.
| $$ \begin{aligned}(5-6i)\cdot(-3+r\cdot2i)& \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle1}{\textcircled {1}} } }}}-15+10ir+18i-12i^2r \xlongequal{ } \\[1 em] & \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle2}{\textcircled {2}} } }}}-12i^2r+10ir+18i-15\end{aligned} $$ | |
| ① | Multiply each term of $ \left( \color{blue}{5-6i}\right) $ by each term in $ \left( -3+2ir\right) $. $$ \left( \color{blue}{5-6i}\right) \cdot \left( -3+2ir\right) = -15+10ir+18i-12i^2r $$ |
| ② | Combine like terms: $$ -12i^2r+10ir+18i-15 = -12i^2r+10ir+18i-15 $$ |
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