| $$ \begin{aligned}4(p^2+9)& \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle1}{\textcircled {1}} } }}}4p^2+36\end{aligned} $$ | |
| ① | Multiply $ \color{blue}{4} $ by $ \left( p^2+9\right) $ $$ \color{blue}{4} \cdot \left( p^2+9\right) = 4p^2+36 $$ |