I guess I figured it out on my own. Since the function is a polynomial it is defined everywhere and therefore has no vertical asymptote.
I have F(x)= x^4 + 4x^3
I need to find out the vertical asymptotes with
lim x-> a+ f(x) = + - infinity and
lim x-> a- f(x) = + - infinity
With a rational function I set the denominator zero and the x-values I get I use as "a"
How does this work for a polynomial?
If I set f(x) = 0 I get for x= 0 and x= 4
I can not figure out what to do next...