Tap the blue circles to see an explanation.
| $$ \begin{aligned}5i\cdot5i& \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle1}{\textcircled {1}} } }}}25i^2 \xlongequal{ } \\[1 em] & \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle2}{\textcircled {2}} } }}}-25\end{aligned} $$ | |
| ① | $$ 5 i \cdot 5 i = 25 i^{1 + 1} = 25 i^2 $$ |
| ② | $$ 25i^2 = 25 \cdot (-1) = -25 $$ |