The problem I'm trying to find the oblique asymptote for is: 8x^3+1/x^2-5x+6

I know the answers to this specific problem(vertical asymptotes at: x=2,x=3; oblique asymptote at:y=x+5) but I don't know how to arrive at the answer for the oblique asymptote for this specific problem. Can anyone help? I know about how to use long division to solve most of these types of problems, but this one I don't know how to achieve the correct answer for the oblique asymptote even with long division.