| $$ \begin{aligned}a^2b+b^2c+c^2a-ab^2-bc^2-ca^2& \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle1}{\textcircled {1}} } }}}a^2b-a^2c-ab^2+ac^2+b^2c-bc^2\end{aligned} $$ | |
| ① | Combine like terms: $$ a^2b-a^2c-ab^2+ac^2+b^2c-bc^2 = a^2b-a^2c-ab^2+ac^2+b^2c-bc^2 $$ |