| $$ \begin{aligned}\frac{x^2-16}{x^2-16+64}& \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle1}{\textcircled {1}} } }}}\frac{x^2-16}{x^2+48}\end{aligned} $$ | |
| ① | Simplify denominator $$ x^2 \color{blue}{-16} + \color{blue}{64} = x^2+ \color{blue}{48} $$ |