Question
Answer
$$5i\cdot4i=-20$$
Explanation
Tap the blue circles to see an explanation.
| $$ \begin{aligned}5i\cdot4i& \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle1}{\textcircled {1}} } }}}20i^2 \xlongequal{ } \\[1 em] & \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle2}{\textcircled {2}} } }}}-20\end{aligned} $$ | |
| ① | $$ 5 i \cdot 4 i = 20 i^{1 + 1} = 20 i^2 $$ |
| ② | $$ 20i^2 = 20 \cdot (-1) = -20 $$ |
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