Question
Answer
$$(-9+5i)(-7i-9)=-35i^2+18i+81$$
Explanation
Tap the blue circles to see an explanation.
| $$ \begin{aligned}(-9+5i)(-7i-9)& \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle1}{\textcircled {1}} } }}}63i+81-35i^2-45i \xlongequal{ } \\[1 em] & \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle2}{\textcircled {2}} } }}}-35i^2+18i+81\end{aligned} $$ | |
| ① | Multiply each term of $ \left( \color{blue}{-9+5i}\right) $ by each term in $ \left( -7i-9\right) $. $$ \left( \color{blue}{-9+5i}\right) \cdot \left( -7i-9\right) = 63i+81-35i^2-45i $$ |
| ② | Combine like terms: $$ \color{blue}{63i} +81-35i^2 \color{blue}{-45i} = -35i^2+ \color{blue}{18i} +81 $$ |
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