| $$ \begin{aligned}15a^2-7a^4-10a^4-5a^4+25a^3+35a^3& \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle1}{\textcircled {1}} } }}}-22a^4+60a^3+15a^2\end{aligned} $$ | |
| ① | Combine like terms: $$ 15a^2 \color{blue}{-7a^4} \color{red}{-10a^4} \color{red}{-5a^4} + \color{green}{25a^3} + \color{green}{35a^3} = \color{red}{-22a^4} + \color{green}{60a^3} +15a^2 $$ |