| $$ \begin{aligned}6v^2(v+7)& \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle1}{\textcircled {1}} } }}}6v^3+42v^2\end{aligned} $$ | |
| ① | Multiply $ \color{blue}{6v^2} $ by $ \left( v+7\right) $ $$ \color{blue}{6v^2} \cdot \left( v+7\right) = 6v^3+42v^2 $$ |