We have indeterminateness of type
oo/oo,
i.e. limit for the numerator is
n→∞lim(n+1)3=∞and limit for the denominator is
n→∞limn3=∞Let's take derivatives of the numerator and denominator until we eliminate indeterninateness.
n→∞lim(n3(n+1)3)=
Let's transform the function under the limit a few
n→∞lim(n3(n+1)3)=
n→∞lim(dndn3dnd(n+1)3)=
n→∞lim(n2(n+1)2)=
n→∞lim(dnd3n2dnd3(n+1)2)=
n→∞lim(6n6n+6)=
n→∞lim(dnd6ndnd(6n+6))=
n→∞lim1=
n→∞lim1=
1It can be seen that we have applied Lopital's rule (we have taken derivatives with respect to the numerator and denominator) 3 time(s)