Question
Answer
$$(-7+2i)\cdot(4-5i)=-10i^2+43i-28$$
Explanation
Tap the blue circles to see an explanation.
| $$ \begin{aligned}(-7+2i)\cdot(4-5i)& \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle1}{\textcircled {1}} } }}}-28+35i+8i-10i^2 \xlongequal{ } \\[1 em] & \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle2}{\textcircled {2}} } }}}-10i^2+43i-28\end{aligned} $$ | |
| ① | Multiply each term of $ \left( \color{blue}{-7+2i}\right) $ by each term in $ \left( 4-5i\right) $. $$ \left( \color{blue}{-7+2i}\right) \cdot \left( 4-5i\right) = -28+35i+8i-10i^2 $$ |
| ② | Combine like terms: $$ -28+ \color{blue}{35i} + \color{blue}{8i} -10i^2 = -10i^2+ \color{blue}{43i} -28 $$ |
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