| $$ \begin{aligned}\frac{10x-90}{x-9}& \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle1}{\textcircled {1}} } }}}10\end{aligned} $$ | |
| ① | Simplify $ \dfrac{10x-90}{x-9} $ to $ 10$. Factor both the denominator and the numerator, then cancel the common factor. $\color{blue}{x-9}$. $$ \begin{aligned} \frac{10x-90}{x-9} & =\frac{ 10 \cdot \color{blue}{ \left( x-9 \right) }}{ 1 \cdot \color{blue}{ \left( x-9 \right) }} = \\[1ex] &= \frac{10}{1} =10 \end{aligned} $$ |