$$ \begin{aligned}\frac{x^2-x-20}{x^2+7x+12}& \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle1}{\textcircled {1}} } }}}\frac{x-5}{x+3}\end{aligned} $$ | |
① | Factor both the denominator and the numerator, then cancel the common factor. $\color{blue}{x+4}$. $$ \begin{aligned} \frac{x^2-x-20}{x^2+7x+12} & =\frac{ \left( x-5 \right) \cdot \color{blue}{ \left( x+4 \right) }}{ \left( x+3 \right) \cdot \color{blue}{ \left( x+4 \right) }} = \\[1ex] &= \frac{x-5}{x+3} \end{aligned} $$ |