Question
Answer
$$4i\cdot(-2+7i)=-8i-28$$
Explanation
Tap the blue circles to see an explanation.
| $$ \begin{aligned}4i\cdot(-2+7i)& \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle1}{\textcircled {1}} } }}}-8i+28i^2 \xlongequal{ } \\[1 em] & \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle2}{\textcircled {2}} } }}}-8i-28\end{aligned} $$ | |
| ① | Multiply $ \color{blue}{4i} $ by $ \left( -2+7i\right) $ $$ \color{blue}{4i} \cdot \left( -2+7i\right) = -8i+28i^2 $$ |
| ② | $$ 28i^2 = 28 \cdot (-1) = -28 $$ |
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