Question
Answer
$$(-4-5i)\cdot(9+2i)=-10i^2-53i-36$$
Explanation
Tap the blue circles to see an explanation.
| $$ \begin{aligned}(-4-5i)\cdot(9+2i)& \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle1}{\textcircled {1}} } }}}-36-8i-45i-10i^2 \xlongequal{ } \\[1 em] & \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle2}{\textcircled {2}} } }}}-10i^2-53i-36\end{aligned} $$ | |
| ① | Multiply each term of $ \left( \color{blue}{-4-5i}\right) $ by each term in $ \left( 9+2i\right) $. $$ \left( \color{blue}{-4-5i}\right) \cdot \left( 9+2i\right) = -36-8i-45i-10i^2 $$ |
| ② | Combine like terms: $$ -36 \color{blue}{-8i} \color{blue}{-45i} -10i^2 = -10i^2 \color{blue}{-53i} -36 $$ |
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