Question
Answer
$$(7+4i)\cdot(12-9i)=-36i^2-15i+84$$
Explanation
Tap the blue circles to see an explanation.
| $$ \begin{aligned}(7+4i)\cdot(12-9i)& \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle1}{\textcircled {1}} } }}}84-63i+48i-36i^2 \xlongequal{ } \\[1 em] & \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle2}{\textcircled {2}} } }}}-36i^2-15i+84\end{aligned} $$ | |
| ① | Multiply each term of $ \left( \color{blue}{7+4i}\right) $ by each term in $ \left( 12-9i\right) $. $$ \left( \color{blue}{7+4i}\right) \cdot \left( 12-9i\right) = 84-63i+48i-36i^2 $$ |
| ② | Combine like terms: $$ 84 \color{blue}{-63i} + \color{blue}{48i} -36i^2 = -36i^2 \color{blue}{-15i} +84 $$ |
This page was created using
Complex Expression calculator