| $$ \begin{aligned}10x^2y+4xy^2-10x+x+6y-50& \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle1}{\textcircled {1}} } }}}10x^2y+4xy^2-9x+6y-50\end{aligned} $$ | |
| ① | Combine like terms: $$ 10x^2y+4xy^2 \color{blue}{-10x} + \color{blue}{x} +6y-50 = 10x^2y+4xy^2 \color{blue}{-9x} +6y-50 $$ |