when the rational function becomes undefined in this case when becomes then you have a vertical asymptote. so there is vertical asymptotes at

also, since f(x)=0 has no solutions, the graph a horizonal asymptote at y=0

if the degree of the denominator is greater that the degree of the numerator, the x-axis is the horzontal asymptote

also, what appears sometimes to be asymptotes on a graphing calculator is really just a line going from point to point where there really is a hole in the graph