If or , where f and g are differentiable and exists, this limit coincides with .
To apply the L'Hôpital's rule, there must be a limit in the form , where a can be a number or infinite, and have the indeterminate forms:
Infinity Minus Infinity
For the indeterminate form of infinity minus infinity, the fractions put themselves into a common denominator.
Zero Times Infinity
The indeterminate form of zero times infinity is transformed as follows:
In the indeterminate forms zero to the power of zero, infinity to the power of zero and one to the power of infinity; make the following transformations: