## Precalculus (6th Edition) Blitzer

If the graph of a function f increases or decreases without bound as x approaches a, then the line $x=a$ is a vertical asymptote of the graph of f. the equation of such a line for the graph of $f\left( x \right)=\frac{2}{x+5}$ is $x=-5$.
The line $x=a$ is a vertical asymptote of the graph of a function f if $f\left( x \right)$ increases or decreases without bound as x approaches a. For the function $f\left( x \right)=\frac{2}{x+5}$ there are no common factors in the numerator and the denominator. The zero of the denominator is -5. Thus, $x=-5$ is the vertical asymptote for the graph of f.