Question
Answer
$$-20i\cdot(-2+4i)=40i+80$$
Explanation
Tap the blue circles to see an explanation.
| $$ \begin{aligned}-20i\cdot(-2+4i)& \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle1}{\textcircled {1}} } }}}-(-40i+80i^2) \xlongequal{ } \\[1 em] & \xlongequal{ }-(-40i-80) \xlongequal{ } \\[1 em] & \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle2}{\textcircled {2}} } }}}40i+80\end{aligned} $$ | |
| ① | Multiply $ \color{blue}{20i} $ by $ \left( -2+4i\right) $ $$ \color{blue}{20i} \cdot \left( -2+4i\right) = -40i+80i^2 $$ |
| ② | Remove the parentheses by changing the sign of each term within them. $$ - \left(-40i-80 \right) = 40i+80 $$ |
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