Answer
$$4(-2i)\cdot(1-2i)=-8i-16$$
Explanation
Tap the blue circles to see an explanation.
| $$ \begin{aligned}4(-2i)\cdot(1-2i)& \xlongequal{ }-8i\cdot(1-2i) \xlongequal{ } \\[1 em] & \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle1}{\textcircled {1}} } }}}-8i+16i^2 \xlongequal{ } \\[1 em] & \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle2}{\textcircled {2}} } }}}-8i-16\end{aligned} $$ | |
| ① | Multiply $ \color{blue}{-8i} $ by $ \left( 1-2i\right) $ $$ \color{blue}{-8i} \cdot \left( 1-2i\right) = -8i+16i^2 $$ |
| ② | $$ 16i^2 = 16 \cdot (-1) = -16 $$ |
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