| $$ \begin{aligned}4h(3h-5)& \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle1}{\textcircled {1}} } }}}12h^2-20h\end{aligned} $$ | |
| ① | Multiply $ \color{blue}{4h} $ by $ \left( 3h-5\right) $ $$ \color{blue}{4h} \cdot \left( 3h-5\right) = 12h^2-20h $$ |