Tap the blue circles to see an explanation.
| $$ \begin{aligned}-3ii& \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle1}{\textcircled {1}} } }}}-3i^2 \xlongequal{ } \\[1 em] & \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle2}{\textcircled {2}} } }}}3\end{aligned} $$ | |
| ① | $$ 3 i i = 3 i^{1 + 1} = 3 i^2 $$ |
| ② | $$ -3i^2 = -3 \cdot (-1) = 3 $$ |