Which of the following functions has an oblique asymptote?
f(x)=1x2+1f(x) = \frac{1}{x^2+1}f(x)=x2+11
f(x)=x2+1x−1f(x) = \frac{x^2+1}{x-1}f(x)=x−1x2+1
f(x)=x+1x2+1f(x) = \frac{x+1}{x^2+1}f(x)=x2+1x+1
f(x)=2x3x3−1f(x) = \frac{2x^3}{x^3-1}f(x)=x3−12x3