Let's take the limit x→∞lim(−x3) Let's divide numerator and denominator by x: x→∞lim(−x3) = x→∞lim(1(−1)3x1) Do Replacement u=x1 then x→∞lim(1(−1)3x1)=u→0+lim(−3u) = −0=0
The final answer: x→∞lim(−x3)=0
Lopital's rule
There is no sense to apply Lopital's rule to this function since there is no indeterminateness of 0/0 or oo/oo type