| $$ \begin{aligned}6c^2(6c^2-6c+6)& \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle1}{\textcircled {1}} } }}}36c^4-36c^3+36c^2\end{aligned} $$ | |
| ① | Multiply $ \color{blue}{6c^2} $ by $ \left( 6c^2-6c+6\right) $ $$ \color{blue}{6c^2} \cdot \left( 6c^2-6c+6\right) = 36c^4-36c^3+36c^2 $$ |