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