| $$ \begin{aligned}6a^4c+8ac^2-4a^4c-15-10ac^2& \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle1}{\textcircled {1}} } }}}2a^4c-2ac^2-15\end{aligned} $$ | |
| ① | Combine like terms: $$ \color{blue}{6a^4c} + \color{red}{8ac^2} \color{blue}{-4a^4c} -15 \color{red}{-10ac^2} = \color{blue}{2a^4c} \color{red}{-2ac^2} -15 $$ |