| $$ \begin{aligned}\frac{x^2-16}{x^2-8x+16}& \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle1}{\textcircled {1}} } }}}\frac{x+4}{x-4}\end{aligned} $$ | |
| ① | Simplify $ \dfrac{x^2-16}{x^2-8x+16} $ to $ \dfrac{x+4}{x-4} $. Factor both the denominator and the numerator, then cancel the common factor. $\color{blue}{x-4}$. $$ \begin{aligned} \frac{x^2-16}{x^2-8x+16} & =\frac{ \left( x+4 \right) \cdot \color{blue}{ \left( x-4 \right) }}{ \left( x-4 \right) \cdot \color{blue}{ \left( x-4 \right) }} = \\[1ex] &= \frac{x+4}{x-4} \end{aligned} $$ |