Which expression represents the vertical asymptote of f(x)=x−1x2+2x−3f(x) = \frac{x-1}{x^2+2x-3}f(x)=x2+2x−3x−1?
x=1x=1x=1
x=−3x=-3x=−3
x=1,x=−3x=1, x=-3x=1,x=−3
No vertical asymptote