Answer
$$(1-5i)\cdot(-7+8i)=-40i^2+43i-7$$
Explanation
Tap the blue circles to see an explanation.
| $$ \begin{aligned}(1-5i)\cdot(-7+8i)& \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle1}{\textcircled {1}} } }}}-7+8i+35i-40i^2 \xlongequal{ } \\[1 em] & \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle2}{\textcircled {2}} } }}}-40i^2+43i-7\end{aligned} $$ | |
| ① | Multiply each term of $ \left( \color{blue}{1-5i}\right) $ by each term in $ \left( -7+8i\right) $. $$ \left( \color{blue}{1-5i}\right) \cdot \left( -7+8i\right) = -7+8i+35i-40i^2 $$ |
| ② | Combine like terms: $$ -7+ \color{blue}{8i} + \color{blue}{35i} -40i^2 = -40i^2+ \color{blue}{43i} -7 $$ |
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