| $$ \begin{aligned}\frac{x^2+3x-70}{x+10}& \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle1}{\textcircled {1}} } }}}x-7\end{aligned} $$ | |
| ① | Simplify $ \dfrac{x^2+3x-70}{x+10} $ to $ x-7$. Factor both the denominator and the numerator, then cancel the common factor. $\color{blue}{x+10}$. $$ \begin{aligned} \frac{x^2+3x-70}{x+10} & =\frac{ \left( x-7 \right) \cdot \color{blue}{ \left( x+10 \right) }}{ 1 \cdot \color{blue}{ \left( x+10 \right) }} = \\[1ex] &= \frac{x-7}{1} =x-7 \end{aligned} $$ |