We have indeterminateness of type
-oo/oo,
i.e. limit for the numerator is
x→−∞limx=−∞and limit for the denominator is
x→−∞lime−x=∞Let's take derivatives of the numerator and denominator until we eliminate indeterninateness.
x→−∞lim(exx)=
Let's transform the function under the limit a few
x→−∞lim(xex)=
x→−∞lim(dxde−xdxdx)=
x→−∞lim(−ex)=
x→−∞lim(−ex)=
0It can be seen that we have applied Lopital's rule (we have taken derivatives with respect to the numerator and denominator) 1 time(s)