Question
Answer
$$7i\cdot(3+10i)=21i-70$$
Explanation
Tap the blue circles to see an explanation.
| $$ \begin{aligned}7i\cdot(3+10i)& \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle1}{\textcircled {1}} } }}}21i+70i^2 \xlongequal{ } \\[1 em] & \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle2}{\textcircled {2}} } }}}21i-70\end{aligned} $$ | |
| ① | Multiply $ \color{blue}{7i} $ by $ \left( 3+10i\right) $ $$ \color{blue}{7i} \cdot \left( 3+10i\right) = 21i+70i^2 $$ |
| ② | $$ 70i^2 = 70 \cdot (-1) = -70 $$ |
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