| $$ \begin{aligned}y^3+9xy^2+24x^2y+16x^3-cx\cdot3-1& \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle1}{\textcircled {1}} } }}}16x^3+24x^2y+9xy^2+y^3-3cx-1\end{aligned} $$ | |
| ① | Combine like terms: $$ 16x^3+24x^2y+9xy^2+y^3-3cx-1 = 16x^3+24x^2y+9xy^2+y^3-3cx-1 $$ |