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