The line x = a is called a Vertical Asymptote of the curve y = f(x) if at least one of the following statements is true.
For rational functions, vertical asymptotes are vertical lines that correspond to the zeroes points of the denominator.
Given rational function, f(x)
Write f(x) in reduced form
f(x) - c is a factor in the denominator then x = c is the vertical asymptote.