| $$ \begin{aligned}\frac{x^2-1}{x^2+5x-6}& \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle1}{\textcircled {1}} } }}}\frac{x+1}{x+6}\end{aligned} $$ | |
| ① | Simplify $ \dfrac{x^2-1}{x^2+5x-6} $ to $ \dfrac{x+1}{x+6} $. Factor both the denominator and the numerator, then cancel the common factor. $\color{blue}{x-1}$. $$ \begin{aligned} \frac{x^2-1}{x^2+5x-6} & =\frac{ \left( x+1 \right) \cdot \color{blue}{ \left( x-1 \right) }}{ \left( x+6 \right) \cdot \color{blue}{ \left( x-1 \right) }} = \\[1ex] &= \frac{x+1}{x+6} \end{aligned} $$ |