We have indeterminateness of type
oo/oo,
i.e. limit for the numerator is
$$\lim_{x \to \infty}\left(x^{3} + 3 x^{2} + 3 x + 1\right) = \infty$$
and limit for the denominator is
$$\lim_{x \to \infty} x^{3} = \infty$$
Let's take derivatives of the numerator and denominator until we eliminate indeterninateness.
$$\lim_{x \to \infty} \left(1 + \frac{1}{x}\right)^{3}$$
=
Let's transform the function under the limit a few
$$\lim_{x \to \infty}\left(\frac{\left(x + 1\right)^{3}}{x^{3}}\right)$$
=
$$\lim_{x \to \infty}\left(\frac{\frac{d}{d x} \left(x^{3} + 3 x^{2} + 3 x + 1\right)}{\frac{d}{d x} x^{3}}\right)$$
=
$$\lim_{x \to \infty}\left(\frac{3 x^{2} + 6 x + 3}{3 x^{2}}\right)$$
=
$$\lim_{x \to \infty}\left(\frac{\frac{d}{d x} \left(3 x^{2} + 6 x + 3\right)}{\frac{d}{d x} 3 x^{2}}\right)$$
=
$$\lim_{x \to \infty}\left(\frac{6 x + 6}{6 x}\right)$$
=
$$\lim_{x \to \infty}\left(\frac{\frac{d}{d x} \left(6 x + 6\right)}{\frac{d}{d x} 6 x}\right)$$
=
$$\lim_{x \to \infty} 1$$
=
$$\lim_{x \to \infty} 1$$
=
$$1$$
It can be seen that we have applied Lopital's rule (we have taken derivatives with respect to the numerator and denominator) 3 time(s)