Question
Answer
$$(7+7i)\cdot(-10+3i)=21i^2-49i-70$$
Explanation
Tap the blue circles to see an explanation.
| $$ \begin{aligned}(7+7i)\cdot(-10+3i)& \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle1}{\textcircled {1}} } }}}-70+21i-70i+21i^2 \xlongequal{ } \\[1 em] & \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle2}{\textcircled {2}} } }}}21i^2-49i-70\end{aligned} $$ | |
| ① | Multiply each term of $ \left( \color{blue}{7+7i}\right) $ by each term in $ \left( -10+3i\right) $. $$ \left( \color{blue}{7+7i}\right) \cdot \left( -10+3i\right) = -70+21i-70i+21i^2 $$ |
| ② | Combine like terms: $$ -70+ \color{blue}{21i} \color{blue}{-70i} +21i^2 = 21i^2 \color{blue}{-49i} -70 $$ |
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