| $$ \begin{aligned}2^2+16x& \xlongequal{ }4+16x \xlongequal{ } \\[1 em] & \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle1}{\textcircled {1}} } }}}16x+4\end{aligned} $$ | |
| ① | Combine like terms: $$ 16x+4 = 16x+4 $$ |