If the degree of the numerator is less than the degree of the denominator, then the horizontal asymptote will be y = 0
If the degree of the numerator equals the degree of the denominator, then the horizontal asymptote will be y = a/b where "a" is the coefficient of the highest term of the numerator and "b" is the coefficient of the highest degree term in the denominator. So for
The degrees are 3's and the "a" is 12 and the "b" is 18. So the horizontal asymptote would be: which reduces to
If the degree of the numerator is greater than the degree of the denominator, then there is no horizontal asymptote. (There will, however, be an asymptote that is not horizontal or vertical.)
Your numerator's degree is 4 and your denominator's degree is 1. So there will not be a horizontal asymptote.