is $\displaystyle \frac{1}{x^2}$ a vertical asymptote? Part of the definition is that the fraction must be a rational function, which means a function that can be expressed as a ratio of two polynomials. $\displaystyle \frac{1}{x^2}$ cannot be expressed as a ratio of two polynomials as far as I can tell. So, am I correct that it is not a vertical asymptote?

What is the most efficient way to identify a vertical asymptote?