Question
Answer
$$-4\cdot(-4+i)\cdot(-1-4i)=-60i-32$$
Explanation
Tap the blue circles to see an explanation.
| $$ \begin{aligned}-4\cdot(-4+i)\cdot(-1-4i)& \xlongequal{ }-(-16+4i)\cdot(-1-4i) \xlongequal{ } \\[1 em] & \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle1}{\textcircled {1}} } }}}-(16+64i-4i-16i^2) \xlongequal{ } \\[1 em] & \xlongequal{ }-(-16i^2+60i+16) \xlongequal{ } \\[1 em] & \xlongequal{ }-(16+60i+16) \xlongequal{ } \\[1 em] & \xlongequal{ }-(60i+32) \xlongequal{ } \\[1 em] & \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle2}{\textcircled {2}} } }}}-60i-32\end{aligned} $$ | |
| ① | Multiply each term of $ \left( \color{blue}{-16+4i}\right) $ by each term in $ \left( -1-4i\right) $. $$ \left( \color{blue}{-16+4i}\right) \cdot \left( -1-4i\right) = 16+64i-4i-16i^2 $$ |
| ② | Remove the parentheses by changing the sign of each term within them. $$ - \left(60i+32 \right) = -60i-32 $$ |
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