| $$ \begin{aligned}0.1x\cdot60x& \xlongequal{ }0x\cdot60x \xlongequal{ } \\[1 em] & \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle1}{\textcircled {1}} } }}}0x^2\end{aligned} $$ | |
| ① | $$ 0 x \cdot 60 x = 0 x^{1 + 1} = 0 x^2 $$ |