Question
Answer
$$-9i(-9i+4)+3\cdot(8+8i)=-12i-57$$
Explanation
Tap the blue circles to see an explanation.
| $$ \begin{aligned}-9i(-9i+4)+3\cdot(8+8i)& \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle1}{\textcircled {1}} } }}}-(-81i^2+36i)+24+24i \xlongequal{ } \\[1 em] & \xlongequal{ }-(81+36i)+24+24i \xlongequal{ } \\[1 em] & \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle2}{\textcircled {2}} } }}}-81-36i+24+24i \xlongequal{ } \\[1 em] & \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle3}{\textcircled {3}} } }}}-12i-57\end{aligned} $$ | |
| ① | Multiply $ \color{blue}{9i} $ by $ \left( -9i+4\right) $ $$ \color{blue}{9i} \cdot \left( -9i+4\right) = -81i^2+36i $$Multiply $ \color{blue}{3} $ by $ \left( 8+8i\right) $ $$ \color{blue}{3} \cdot \left( 8+8i\right) = 24+24i $$ |
| ② | Remove the parentheses by changing the sign of each term within them. $$ - \left(81+36i \right) = -81-36i $$ |
| ③ | Combine like terms: $$ \color{blue}{-81} \color{red}{-36i} + \color{blue}{24} + \color{red}{24i} = \color{red}{-12i} \color{blue}{-57} $$ |
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