Question
Answer
$$(-1+3i)\cdot(7+5i)=15i^2+16i-7$$
Explanation
Tap the blue circles to see an explanation.
| $$ \begin{aligned}(-1+3i)\cdot(7+5i)& \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle1}{\textcircled {1}} } }}}-7-5i+21i+15i^2 \xlongequal{ } \\[1 em] & \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle2}{\textcircled {2}} } }}}15i^2+16i-7\end{aligned} $$ | |
| ① | Multiply each term of $ \left( \color{blue}{-1+3i}\right) $ by each term in $ \left( 7+5i\right) $. $$ \left( \color{blue}{-1+3i}\right) \cdot \left( 7+5i\right) = -7-5i+21i+15i^2 $$ |
| ② | Combine like terms: $$ -7 \color{blue}{-5i} + \color{blue}{21i} +15i^2 = 15i^2+ \color{blue}{16i} -7 $$ |
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