| $$ \begin{aligned}\frac{x^2-17x+70}{x^2-18x+80}& \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle1}{\textcircled {1}} } }}}\frac{x-7}{x-8}\end{aligned} $$ | |
| ① | Simplify $ \dfrac{x^2-17x+70}{x^2-18x+80} $ to $ \dfrac{x-7}{x-8} $. Factor both the denominator and the numerator, then cancel the common factor. $\color{blue}{x-10}$. $$ \begin{aligned} \frac{x^2-17x+70}{x^2-18x+80} & =\frac{ \left( x-7 \right) \cdot \color{blue}{ \left( x-10 \right) }}{ \left( x-8 \right) \cdot \color{blue}{ \left( x-10 \right) }} = \\[1ex] &= \frac{x-7}{x-8} \end{aligned} $$ |