So the limit as x approaches infinity of all of this, it's actually unbounded. It's infinity. And a kind of obvious way of seeing that right from the get-go is to realize that the numerator has a 4th degree term, while the highest degree term in the denominator is only a 3rd degree term. So the numerator is going to grow far faster than the denominator. So if the numerator is going far faster than the denominator, you're going to approach infinity in this case. If the numerator is going far slower than the denominator, if the denominator is going far faster than the numerator, like this case, you are then approaching 0. So hopefully you find that a little bit useful.