Answer
To the forms $0/0$ and $\pm \infty/\pm \infty$.
Work Step by Step
It applies certainly directly to $0/0$ form.
But the forms $\pm\infty/\pm\infty$ can be transformed as
$$\frac{f}{g}=\frac{\frac{1}{g}}{\frac{1}{f}}=\frac{1/\infty}{1/\infty}=0/0$$
so we can directly apply the rule to these forms as well.
