Answer
$$(-5i)\cdot5i\cdot(-4-i)=-25i-100$$
Explanation
Tap the blue circles to see an explanation.
| $$ \begin{aligned}(-5i)\cdot5i\cdot(-4-i)& \xlongequal{ }-25i^2\cdot(-4-i) \xlongequal{ } \\[1 em] & \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle1}{\textcircled {1}} } }}}25\cdot(-4-i) \xlongequal{ } \\[1 em] & \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle2}{\textcircled {2}} } }}}-100-25i \xlongequal{ } \\[1 em] & \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle3}{\textcircled {3}} } }}}-25i-100\end{aligned} $$ | |
| ① | $$ -25i^2 = -25 \cdot (-1) = 25 $$ |
| ② | Multiply $ \color{blue}{25} $ by $ \left( -4-i\right) $ $$ \color{blue}{25} \cdot \left( -4-i\right) = -100-25i $$ |
| ③ | Combine like terms: $$ -25i-100 = -25i-100 $$ |
This page was created using
Complex Expression calculator