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