Question
Answer
$$(4-3i)\cdot(7+i)=-3i^2-17i+28$$
Explanation
Tap the blue circles to see an explanation.
| $$ \begin{aligned}(4-3i)\cdot(7+i)& \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle1}{\textcircled {1}} } }}}28+4i-21i-3i^2 \xlongequal{ } \\[1 em] & \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle2}{\textcircled {2}} } }}}-3i^2-17i+28\end{aligned} $$ | |
| ① | Multiply each term of $ \left( \color{blue}{4-3i}\right) $ by each term in $ \left( 7+i\right) $. $$ \left( \color{blue}{4-3i}\right) \cdot \left( 7+i\right) = 28+4i-21i-3i^2 $$ |
| ② | Combine like terms: $$ 28+ \color{blue}{4i} \color{blue}{-21i} -3i^2 = -3i^2 \color{blue}{-17i} +28 $$ |
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