| $$ \begin{aligned}(x^2+7)(4x-7)& \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle1}{\textcircled {1}} } }}}4x^3-7x^2+28x-49\end{aligned} $$ | |
| ① | Multiply each term of $ \left( \color{blue}{x^2+7}\right) $ by each term in $ \left( 4x-7\right) $. $$ \left( \color{blue}{x^2+7}\right) \cdot \left( 4x-7\right) = 4x^3-7x^2+28x-49 $$ |