| $$ \begin{aligned}6y-5x^4y+6y^2+y-7y^2-4x^4y& \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle1}{\textcircled {1}} } }}}-9x^4y-y^2+7y\end{aligned} $$ | |
| ① | Combine like terms: $$ \color{blue}{6y} \color{red}{-5x^4y} + \color{green}{6y^2} + \color{blue}{y} \color{green}{-7y^2} \color{red}{-4x^4y} = \color{red}{-9x^4y} \color{green}{-y^2} + \color{blue}{7y} $$ |