Answer
$$(-7-4i)\cdot(-12-7i)=28i^2+97i+84$$
Explanation
Tap the blue circles to see an explanation.
| $$ \begin{aligned}(-7-4i)\cdot(-12-7i)& \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle1}{\textcircled {1}} } }}}84+49i+48i+28i^2 \xlongequal{ } \\[1 em] & \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle2}{\textcircled {2}} } }}}28i^2+97i+84\end{aligned} $$ | |
| ① | Multiply each term of $ \left( \color{blue}{-7-4i}\right) $ by each term in $ \left( -12-7i\right) $. $$ \left( \color{blue}{-7-4i}\right) \cdot \left( -12-7i\right) = 84+49i+48i+28i^2 $$ |
| ② | Combine like terms: $$ 84+ \color{blue}{49i} + \color{blue}{48i} +28i^2 = 28i^2+ \color{blue}{97i} +84 $$ |
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