| $$ \begin{aligned}4x^2-8x^2& \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle1}{\textcircled {1}} } }}}-4x^2\end{aligned} $$ | |
| ① | Combine like terms: $$ \color{blue}{4x^2} \color{blue}{-8x^2} = \color{blue}{-4x^2} $$ |