Question
Answer
$$-5i\cdot(2+8i)=-10i+40$$
Explanation
Tap the blue circles to see an explanation.
| $$ \begin{aligned}-5i\cdot(2+8i)& \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle1}{\textcircled {1}} } }}}-(10i+40i^2) \xlongequal{ } \\[1 em] & \xlongequal{ }-(10i-40) \xlongequal{ } \\[1 em] & \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle2}{\textcircled {2}} } }}}-10i+40\end{aligned} $$ | |
| ① | Multiply $ \color{blue}{5i} $ by $ \left( 2+8i\right) $ $$ \color{blue}{5i} \cdot \left( 2+8i\right) = 10i+40i^2 $$ |
| ② | Remove the parentheses by changing the sign of each term within them. $$ - \left(10i-40 \right) = -10i+40 $$ |
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