Question
Answer
$$(9i-2)(4i+1)=36i^2+i-2$$
Explanation
Tap the blue circles to see an explanation.
| $$ \begin{aligned}(9i-2)(4i+1)& \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle1}{\textcircled {1}} } }}}36i^2+9i-8i-2 \xlongequal{ } \\[1 em] & \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle2}{\textcircled {2}} } }}}36i^2+i-2\end{aligned} $$ | |
| ① | Multiply each term of $ \left( \color{blue}{9i-2}\right) $ by each term in $ \left( 4i+1\right) $. $$ \left( \color{blue}{9i-2}\right) \cdot \left( 4i+1\right) = 36i^2+9i-8i-2 $$ |
| ② | Combine like terms: $$ 36i^2+ \color{blue}{9i} \color{blue}{-8i} -2 = 36i^2+ \color{blue}{i} -2 $$ |
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