Question
Answer
$$(-2+8i)\cdot(3-9i)=-72i^2+42i-6$$
Explanation
Tap the blue circles to see an explanation.
| $$ \begin{aligned}(-2+8i)\cdot(3-9i)& \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle1}{\textcircled {1}} } }}}-6+18i+24i-72i^2 \xlongequal{ } \\[1 em] & \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle2}{\textcircled {2}} } }}}-72i^2+42i-6\end{aligned} $$ | |
| ① | Multiply each term of $ \left( \color{blue}{-2+8i}\right) $ by each term in $ \left( 3-9i\right) $. $$ \left( \color{blue}{-2+8i}\right) \cdot \left( 3-9i\right) = -6+18i+24i-72i^2 $$ |
| ② | Combine like terms: $$ -6+ \color{blue}{18i} + \color{blue}{24i} -72i^2 = -72i^2+ \color{blue}{42i} -6 $$ |
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