Calculus AB : Apply Intermediate Value Theorem

Study concepts, example questions & explanations for Calculus AB

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Example Questions

Example Question #1 : Apply Intermediate Value Theorem

Which of the following does NOT satisfy the conditions required to apply the Intermediate Value Theorem to a function  on the interval ?

Possible Answers:

The function f must be continuous along  to apply Intermediate Value Theorem

Intermediate Value Theorem considers points within the interval 

Intermediate Value Theorem cannot be applied outside of the interval 

 

Intermediate Value Theorem can be used when 

Correct answer:

Intermediate Value Theorem can be used when 

Explanation:

Intermediate Value Theorem states that if the function  is continuous and has a domain containing the interval , then at some number  within the interval  the function will take on a value  that is between the values of  and .

The conditions that must be satisfied in order to use Intermediate Value Theorem include that the function must be continuous and the number  must be within the interval . However,  cannot equal .

Therefore, the answer choice “Intermediate Value Theorem can be used when ” does not satisfy the necessary conditions and is the correct answer for this question.

 

Example Question #1 : Apply Intermediate Value Theorem

Using Intermediate Value Theorem to analyze a continuous function, what can be deduced if a polynomial changes signs within an interval?

Possible Answers:

The function is not differentiable within that interval

The function is not continuous within that interval

 

There is a local maximum between the endpoints of that interval

There is a zero between the endpoints of that interval

Correct answer:

There is a zero between the endpoints of that interval

Explanation:

Intermediate Value Theorem is only true with continuous, differentiable functions, thus eliminating the answer choices “The function is not continuous within that interval” and “The function is not differentiable within that interval.” There is not necessarily a local maximum or minimum contained in the interval either. That leaves the correct answer choice, “There is a zero between the endpoints of that interval.” If the polynomial is changing signs and meets the requirements for Intermediate Value Theorem, it must cross the  axis at some point within the interval.

Example Question #1 : Apply Intermediate Value Theorem

What theorem could you use to show that a polynomial has a root on a given interval?

Possible Answers:

Mean Value Theorem for Derivatives

Fundamental Theorem of Calculus

Extreme Value Theorem

Intermediate Value Theorem

 

Correct answer:

Intermediate Value Theorem

 

Explanation:

A polynomial has a zero or root when it crosses the  axis. For a given interval , if a and b have different signs (for instance, if  is negative and  is positive), then by Intermediate Value Theorem there must be a value of zero between  and . Therefore, Intermediate Value Theorem is the correct answer.

Example Question #1 : Apply Intermediate Value Theorem

Using the continuous function  and the interval , which of the following correctly identifies why the Intermediate Value Theorem is useful?

Possible Answers:

The Intermediate Value Theorem tells you how many times the function  repeats a value as it progresses from  to 

The Intermediate Value Theorem states that somewhere between  and  there exists a value , with 

The Intermediate Value Theorem can identify the value of  that the function takes on as it passes from  to 

The Intermediate Value Theorem is not useful

Correct answer:

The Intermediate Value Theorem states that somewhere between  and  there exists a value , with 

Explanation:

The Intermediate Value Theorem tells us that a value between  and  exists, but it does not provide any information on what that value is. This eliminates two of the four answer choices  - “The Intermediate Value Theorem can identify the value of  that the function takes on as it passes from  to ” and “The Intermediate Value Theorem tells you how many times the function  repeats a value as it progresses from   to .”

The Intermediate Value Theorem is useful because it can help identify when there are roots or zeros; an example of this is if a polynomial switches signs, Intermediate Value Theorem tells us there is a zero between those values.

From this, we can conclude that the correct answer is “The Intermediate Value Theorem states that somewhere between  and  there exists a value , with .”

 

Example Question #1 : Apply Intermediate Value Theorem

In which interval does  have a root?

Possible Answers:

Correct answer:

Explanation:

Graphing  on cartesian coordinates reveals that the function is continuous and crosses the  axis at a value within the interval

 

Furthermore, setting  produces a negative value for the function, while setting  produces a positive value, as seen below:

 

Because the function is a polynomial, the function is continuous. By Intermediate Value Theorem, if the function changes signs within this interval, there must be a root present within the interval.

 

Example Question #3 : Apply Intermediate Value Theorem

In which interval does the function  NOT necessarily have a root?

Possible Answers:

Correct answer:

Explanation:

Because the function is a polynomial, the function is continuous. By Intermediate Value Theorem, if the function changes signs within this interval, there must be a root present within the interval. 

 

To apply Intermediate Value Theorem to the function , the function can be evaluated at each of the given bounds. 

 

For instance, if the function is evaluated at  and , the following is obtained:

 

 

For the intervals , , and , there is a change in sign within the interval.

 

Because the function does not change in sign within the interval , we cannot conclude by Intermediate Value Theorem whether there is a root contained in the interval or not. Thus,  is the correct answer.

 

Example Question #1 : Apply Intermediate Value Theorem

Can Intermediate Value Theorem be applied to the function  within the interval ?

Possible Answers:

Yes, because the function crosses the  axis within the interval 

No, because the function is not continuous

No, because 

Yes, because the function  has a root at 

Correct answer:

No, because 

Explanation:

The required conditions for Intermediate Value Theorem include the function must be continuous and cannot equal . While there is a root at  for this particular continuous function, this cannot be shown using Intermediate Value Theorem. The function does not cross the  axis, thus eliminating that particular answer choice. The correct answer is “No, because .” Since one of the conditions for Intermediate Value Theorem is that cannot equal , by graphing  we can see that this requirement is not met.

Example Question #3 : Apply Intermediate Value Theorem

What can be concluded by using Intermediate Value Theorem for the function  on the interval ?

Possible Answers:

There are two roots on this polynomial located between  and 

The requirements for Intermediate Value Theorem are not met

There is a root for this polynomial located between  and 

There is a root for this polynomial at 

Correct answer:

There is a root for this polynomial located between  and 

Explanation:

his function is continuous (as it is a polynomial) and ; therefore, the required conditions for Intermediate Value Theorem are met. While there is a root at  for this function (as can be seen by graphing the polynomial), Intermediate Value Theorem does not state where this root will be exactly, nor does it state how many roots there might be. Thus, the conclusion that can be made by IVT is that there is a root for this polynomial located somewhere between  and .

Example Question #2 : Apply Intermediate Value Theorem

Let . Is there a number  between  and  such that ?

Possible Answers:

Yes, as shown by the Fundamental Theorem of Calculus

No, Intermediate Value Theorem cannot determine the exact value of 

No, no number c such that  exists

Yes, as shown by Intermediate Value Theorem

Correct answer:

Yes, as shown by Intermediate Value Theorem

Explanation:

First, determine the values of the function at the bounds. This will allow the correct implementation of the Intermediate Value Theorem.

Because the problem asks to analyze the interval  and , there must be a value , with . Because , by Intermediate Value Theorem there should be a number  between  and  that satisfies the required conditions. Therefore, “Yes, as shown by Intermediate Value Theorem” is the correct  answer.

Example Question #2 : Apply Intermediate Value Theorem

Assume  is continuous on the interval  and has the values listed in the table below. Which of the following values of  guarantees that  has at least two roots?

Q10 table

Possible Answers:

Correct answer:

Explanation:

If , only one root can be guaranteed (at ). 

If , then Intermediate Value Theorem can be applied twice, for  and .

 

This is true because for continuous functions, Intermediate Value Theorem states that a change in sign (ex: from positive to negative) of the function within an interval suggests a root (where the function crosses the  axis) at some point within that interval.

 

 

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