Question
Answer
$$(-8i+5i)\cdot(4-8i)=-12i-24$$
Explanation
Tap the blue circles to see an explanation.
| $$ \begin{aligned}(-8i+5i)\cdot(4-8i)& \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle1}{\textcircled {1}} } }}}-3i\cdot(4-8i) \xlongequal{ } \\[1 em] & \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle2}{\textcircled {2}} } }}}-12i+24i^2 \xlongequal{ } \\[1 em] & \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle3}{\textcircled {3}} } }}}-12i-24\end{aligned} $$ | |
| ① | Combine like terms: $$ \color{blue}{-8i} + \color{blue}{5i} = \color{blue}{-3i} $$ |
| ② | Multiply $ \color{blue}{-3i} $ by $ \left( 4-8i\right) $ $$ \color{blue}{-3i} \cdot \left( 4-8i\right) = -12i+24i^2 $$ |
| ③ | $$ 24i^2 = 24 \cdot (-1) = -24 $$ |
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