Question
Answer
$$(2-8i)\cdot(-5-7i)=56i^2+26i-10$$
Explanation
Tap the blue circles to see an explanation.
| $$ \begin{aligned}(2-8i)\cdot(-5-7i)& \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle1}{\textcircled {1}} } }}}-10-14i+40i+56i^2 \xlongequal{ } \\[1 em] & \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle2}{\textcircled {2}} } }}}56i^2+26i-10\end{aligned} $$ | |
| ① | Multiply each term of $ \left( \color{blue}{2-8i}\right) $ by each term in $ \left( -5-7i\right) $. $$ \left( \color{blue}{2-8i}\right) \cdot \left( -5-7i\right) = -10-14i+40i+56i^2 $$ |
| ② | Combine like terms: $$ -10 \color{blue}{-14i} + \color{blue}{40i} +56i^2 = 56i^2+ \color{blue}{26i} -10 $$ |
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