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