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Example Questions
Example Question #31 : L'hospital's Rule
If you plug in the limit value, the function turns into . Therefore, we are allowed to use l'Hospital's Rule. We start by taking the derivative of both the numerator and the denominator until when you plug in the value of the limit, you do not get something in the form . Luckily, in this case, we only need to take the derivative once. By taking the derivatives separately, we get a new limit:
.
Example Question #31 : L'hospital's Rule
Evaluate:
Limit Does Not Exist
Example Question #33 : L'hospital's Rule
Find the limit using L'Hospital's Rule.
We rewrite the limit as
Substituting yields the indeterminate form
L'Hospital's Rule states that when the limit is in indeterminate form, the limit becomes
For and we solve the limit
and substituting we find that
As such
Example Question #34 : L'hospital's Rule
Find the limit using L'Hospital's Rule.
Substituting yields the indeterminate form
L'Hospital's Rule states that when the limit is in indeterminate form, the limit becomes
For and we solve the limit
and substituting we find that
As such
Example Question #35 : L'hospital's Rule
Evaluate the following limit:
Simply substituting in the given limit will not work:
Because direct substitution yields an indeterminate result, we must apply L'Hospital's rule to the limit:
if and only if and both and exist at .
Here,
and .
Hence,
Example Question #36 : L'hospital's Rule
Evaluate the following limit:
When evaluating the limit using normal methods (substitution), we receive the indeterminate form . When we receive the indeterminate form, we must use L'Hopital's Rule to evaluate the limit. The rule states that
Using the formula above for our limit, we get
The derivatives were found using the following rules:
, ,
Example Question #32 : L'hospital's Rule
Evaluate the limit:
When evaluating the limit using normal methods (substitution), we get the indeterminate form . When this happens, to evaluate the limit we use L'Hopital's Rule, which states that
Using the above formula for our limit, we get
The derivatives were found using the following rule:
Example Question #31 : L'hospital's Rule
Evaluate the following limit, if possible:
The limit does not exist.
To calculate the limit we first plug the limit value into the numerator and denominator of the expression. When we do this we get , which is undefined. We now use L'Hopital's rule which says that if and are differentiable and
,
then
.
We are evaluating the limit
.
In this case we have
and
.
We differentiate both functions and find
and
By L'Hopital's rule
.
When we plug the limit value of 2 into this expression we get 9/3, which simplifies to 3.
Example Question #39 : L'hospital's Rule
Evaluate the following limit, if possible:
.
The limit does not exist.
If we plugged in the limit value, , directly we would get the indeterminate value . We now use L'Hopital's rule which says that if and are differentiable and
,
then
.
The limit we wish to evaluate is
,
so in this case
and
.
We calculate the derivatives of both of these functions and find that
and
.
Thus
.
When we plug the limit value, , into this expression we get , which is .
Example Question #32 : L'hospital's Rule
Evaluate the following limit, if possible:
.
The limit does not exist
The limit does not exist
We will show that the limit does not exist by showing that the limits from the left and right are different.
We will start with the limit from the right. Using the product rule we rewrite the limit
.
We know that
and
so
.
We calculate the limit from the left in the same way and find
.
Thus the two-sided limit does not exist.