| $$ \begin{aligned}\frac{x^3+27}{x^2+2x-3}& \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle1}{\textcircled {1}} } }}}\frac{x^2-3x+9}{x-1}\end{aligned} $$ | |
| ① | Simplify $ \dfrac{x^3+27}{x^2+2x-3} $ to $ \dfrac{x^2-3x+9}{x-1} $. Factor both the denominator and the numerator, then cancel the common factor. $\color{blue}{x+3}$. $$ \begin{aligned} \frac{x^3+27}{x^2+2x-3} & =\frac{ \left( x^2-3x+9 \right) \cdot \color{blue}{ \left( x+3 \right) }}{ \left( x-1 \right) \cdot \color{blue}{ \left( x+3 \right) }} = \\[1ex] &= \frac{x^2-3x+9}{x-1} \end{aligned} $$ |