Question
Answer
$$(9i+6)\cdot(-5+i)=9i^2-39i-30$$
Explanation
Tap the blue circles to see an explanation.
| $$ \begin{aligned}(9i+6)\cdot(-5+i)& \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle1}{\textcircled {1}} } }}}-45i+9i^2-30+6i \xlongequal{ } \\[1 em] & \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle2}{\textcircled {2}} } }}}9i^2-39i-30\end{aligned} $$ | |
| ① | Multiply each term of $ \left( \color{blue}{9i+6}\right) $ by each term in $ \left( -5+i\right) $. $$ \left( \color{blue}{9i+6}\right) \cdot \left( -5+i\right) = -45i+9i^2-30+6i $$ |
| ② | Combine like terms: $$ \color{blue}{-45i} +9i^2-30+ \color{blue}{6i} = 9i^2 \color{blue}{-39i} -30 $$ |
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