| $$ \begin{aligned}2m(6m+6)& \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle1}{\textcircled {1}} } }}}12m^2+12m\end{aligned} $$ | |
| ① | Multiply $ \color{blue}{2m} $ by $ \left( 6m+6\right) $ $$ \color{blue}{2m} \cdot \left( 6m+6\right) = 12m^2+12m $$ |