Question
Answer
$$(7-7i)\cdot(9+3i)=-21i^2-42i+63$$
Explanation
Tap the blue circles to see an explanation.
| $$ \begin{aligned}(7-7i)\cdot(9+3i)& \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle1}{\textcircled {1}} } }}}63+21i-63i-21i^2 \xlongequal{ } \\[1 em] & \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle2}{\textcircled {2}} } }}}-21i^2-42i+63\end{aligned} $$ | |
| ① | Multiply each term of $ \left( \color{blue}{7-7i}\right) $ by each term in $ \left( 9+3i\right) $. $$ \left( \color{blue}{7-7i}\right) \cdot \left( 9+3i\right) = 63+21i-63i-21i^2 $$ |
| ② | Combine like terms: $$ 63+ \color{blue}{21i} \color{blue}{-63i} -21i^2 = -21i^2 \color{blue}{-42i} +63 $$ |
This page was created using
Complex Expression calculator