| $$ \begin{aligned}a+a^2+a^3+a^4+a^5& \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle1}{\textcircled {1}} } }}}a^5+a^4+a^3+a^2+a\end{aligned} $$ | |
| ① | Combine like terms: $$ a^5+a^4+a^3+a^2+a = a^5+a^4+a^3+a^2+a $$ |