| $$ \begin{aligned}\frac{x^2-x-20}{x^3+64}& \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle1}{\textcircled {1}} } }}}\frac{x-5}{x^2-4x+16}\end{aligned} $$ | |
| ① | Simplify $ \dfrac{x^2-x-20}{x^3+64} $ to $ \dfrac{x-5}{x^2-4x+16} $. Factor both the denominator and the numerator, then cancel the common factor. $\color{blue}{x+4}$. $$ \begin{aligned} \frac{x^2-x-20}{x^3+64} & =\frac{ \left( x-5 \right) \cdot \color{blue}{ \left( x+4 \right) }}{ \left( x^2-4x+16 \right) \cdot \color{blue}{ \left( x+4 \right) }} = \\[1ex] &= \frac{x-5}{x^2-4x+16} \end{aligned} $$ |