| $$ \begin{aligned}5x(2x^2-6x+3)& \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle1}{\textcircled {1}} } }}}10x^3-30x^2+15x\end{aligned} $$ | |
| ① | Multiply $ \color{blue}{5x} $ by $ \left( 2x^2-6x+3\right) $ $$ \color{blue}{5x} \cdot \left( 2x^2-6x+3\right) = 10x^3-30x^2+15x $$ |