Question
Answer
$$(-5-7i)\cdot(5+3i)=-21i^2-50i-25$$
Explanation
Tap the blue circles to see an explanation.
| $$ \begin{aligned}(-5-7i)\cdot(5+3i)& \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle1}{\textcircled {1}} } }}}-25-15i-35i-21i^2 \xlongequal{ } \\[1 em] & \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle2}{\textcircled {2}} } }}}-21i^2-50i-25\end{aligned} $$ | |
| ① | Multiply each term of $ \left( \color{blue}{-5-7i}\right) $ by each term in $ \left( 5+3i\right) $. $$ \left( \color{blue}{-5-7i}\right) \cdot \left( 5+3i\right) = -25-15i-35i-21i^2 $$ |
| ② | Combine like terms: $$ -25 \color{blue}{-15i} \color{blue}{-35i} -21i^2 = -21i^2 \color{blue}{-50i} -25 $$ |
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