Limits
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Math › Limits
Evaluate the following limit, if possible:
The limit does not exist.
Explanation
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.
Evaluate the limit:
Explanation
If we evaluate the expression with the limit of , it returns the indeterminate form
.
We can instead use L’Hospital’s Rule to evaluate, using the form:
Where,
Therefore,
If we rewrite the limit with L'Hospital's Rule,
Use L'Hospital's rule to evaluate
.
The limit does not exist.
Explanation
To use L'hospital's rule, evaluate the limit of the numerator of the fraction and the denominator separately. If the result is ,
, or
, take the derivative of the numerator and the denominator separately, and try to evaluate the limit again.
(L'hospital's rule)
(L'hospital's rule again)
(L'hospital's rule again)
Evaluate the following limit, if possible:
.
The limit does not exist.
Explanation
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
.
Evaluate the limit:
Explanation
If we evaluate the expression with the limit of x = 8, it returns the indeterminate form .
We can instead use L’Hospital’s Rule to evaluate, using the form:
Where,
Therefore,
If we rewrite the limit with L'Hospital's Rule,
Evaluate the limit using L'Hopital's Rule.
Undefined
Explanation
L'Hopital's Rule is used to evaluate complicated limits. The rule has you take the derivative of both the numerator and denominator individually to simplify the function. In the given function we take the derivatives the first time and get
.
This still cannot be evaluated properly, so we will take the derivative of both the top and bottom individually again. This time we get
.
Now we have only one x, so we can evaluate when x is infinity. Plug in infinity for x and we get
and
.
So we can simplify the function by remembering that any number divided by infinity gives you zero.
Evaluate the limit using L'Hopital's Rule.
Undefined
Explanation
L'Hopital's Rule is used to evaluate complicated limits. The rule has you take the derivative of both the numerator and denominator individually to simplify the function. In the given function we take the derivatives the first time and get
.
This still cannot be evaluated properly, so we will take the derivative of both the top and bottom individually again. This time we get
.
Now we have only one x, so we can evaluate when x is infinity. Plug in infinity for x and we get
and
.
So we can simplify the function by remembering that any number divided by infinity gives you zero.
Evaluate the limit using L'Hopital's Rule.
Undefined
Explanation
L'Hopital's Rule is used to evaluate complicated limits. The rule has you take the derivative of both the numerator and denominator individually to simplify the function. In the given function we take the derivatives the first time and get
.
This still cannot be evaluated properly, so we will take the derivative of both the top and bottom individually again. This time we get
.
Now we have only one x, so we can evaluate when x is infinity. Plug in infinity for x and we get
and
.
So we can simplify the function by remembering that any number divided by infinity gives you zero.
Evaluate: 
Limit Does Not Exist
Explanation
Evaluate
Explanation
Evaluating the limit to begin with gets us , which is undefined. We can solve this problem using L'Hospital's rule. Taking the derivative of the numerator and denominator with respect to n, we get
. The limit is still undefined. Another application of the rule gets us
, which evaluated at
is in fact
.