Calculus 1 : Intervals

Study concepts, example questions & explanations for Calculus 1

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Example Questions

Example Question #41 : Intervals

Find the intervals on which the following function is increasing:

Possible Answers:

Correct answer:

Explanation:

To find the intervals on which the function is increasing, we must find the intervals where the first derivative is positive. To do this, we must find the first derivative, and find its critical values (at which the first derivative is equal to zero):

The derivative was found using the following rule:

Now, write the intervals of the function for which c is the upper and lower bound:

Note that at the critical value, the derivative is neither positive nor negative.

Now, we analyze the sign of the derivative within each interval; on the first interval, the derivative is always negative, but on the second interval, the first derivative is always positive. In other words, for this set of values -  -  the function is increasing. 

Example Question #41 : Intervals

Determint the intervals on which the following function is increasing:

Possible Answers:

Correct answer:

Explanation:

To determine the intervals on which the function is increasing, we must determine the intervals on which the first derivative of the function is positive. To start, we must find the first derivative:

The derivative was found using the following rule:

The first derivative is a positive constant, therefore the function is increasing on the entire domain, .

Example Question #43 : Intervals

When is the function increasing?

Possible Answers:

Correct answer:

Explanation:

To find where the function is increasing, you must first find the derivative of the function so you can test critical points. The derivative of the function is . Then, set that equal to  to find the critical points. When you set that equal to , you get . Then set up a number line so you can test values to determine when the function is increasing and decreasing. We know it's changing direction at our critical point, . So let's pick a point to the left of  and plug it in to the derivative. I'll pick : . Since the answer is negative, we know that the function is decreasing. Pick a point to the right of 2. I'll pick 3: . Since the answer is positive, the function is increasing. Therefore, the function is increasing from .

Example Question #44 : Intervals

Find the intervals on which the function is increasing:

Possible Answers:

Correct answer:

Explanation:

To find the intervals on which the function is increasing, we must find the intervals on which the first derivative is positive. 

To start, we must first find where the first derivative of the function is zero:

The first derivative was found using the following rule:

Now, set this function equal to zero to get the critical values (values at which the first derivative is equal to zero):

Next, we create the intervals using the critical value as the upper and lower bound of the limits, respectively:

On the first interval, the first derivative is negative, but on the second interval, the first derivative is positive, meaning that on this interval the function is increasing. (Simply plug in any point on the interval into the first derivative function and check the sign.)

The answer is 

Example Question #45 : Intervals

Find the interval on which the following function is increasing.

Possible Answers:

always

never

Correct answer:

Explanation:

To solve, you must first differentiate the function once and then find where the derivative is positive. To differentiate, use the power rule:

Thus,

Now you must find where this is greater than 0, and therefore increasing.

Therefore, our answer is when x is greater than 2. Thus, .

Example Question #46 : Intervals

Find the intervals on which the following function is increasing:

.

Possible Answers:

Correct answer:

Explanation:

We find the region of decreasing of the function by taking the derivative and setting it equal to zero.  Then, we plug numbers to the left and right of the roots into the derivative.  If it is positive, the function is increasing.  

.

If we plug in more negative values, the derivative function is positive.  Therefore, we must be increasing until we get to   In between the roots, the derivative is negative (so, we ignore that).  If we plug values higher than , our derivative function is again positive, so we switch back to increasing after the second root.

Example Question #47 : Intervals

Find the increasing intervals of the following function:

Possible Answers:

The function is never increasing

Correct answer:

Explanation:

To determine the intervals on which the function is increasing, we must find the intervals on which the first derivative is positive.

The first derivative of the function is equal to

and was found using the following rule:

Next, we must find the critical values, at which the first derivative is equal to zero:

Now, using the critical value, we make our intervals:

Note that at the bounds of the interval, the first derivative is neither positive nor negative.

To determine whether the derivative is positive or negative on each interval, simply plug any value on each interval into the first derivative function; on the first interval, the first derivative is negative, and on the second interval it is positive. Thus, the function is increasing on

Example Question #48 : Intervals

Find the intervals on which the following function is increasing:

Possible Answers:

Correct answer:

Explanation:

To find the intervals on which the function is increasing, we must find the intervals on which the first derivative of the function is positive.

The first derivative of the function is

and was found using the following rule:

Next, we must find the critical values, or values at which the first derivative of the function is equal to zero:

Now, using the critical values, we can create the intervals:

Note that at the endpoints of the intervals, the first derivative is neither positive nor negative.

To determine the sign of the first derivative on each interval, simply plug in any value on each interval into the first derivative function and check the sign. On the first interval, the first derivative is positive, on the second it is negative, and on the third it is positive. Thus, the intervals on which the function is increasing are .

Example Question #49 : Intervals

Tell whether g(x) is increasing or decreasing on the interval [0,3], and how you know.

Possible Answers:

The function is decreasing on the interval [0,3], because the first derivative is positive.

The function is increasing on the interval [0,3], because the first derivative is positive.

The function is decreasing on the interval [0,3], because the first derivative is negative.

The function is increasing on the interval [0,3], because the first derivative is negative.

Correct answer:

The function is increasing on the interval [0,3], because the first derivative is positive.

Explanation:

Tell whether g(x) is increasing or decreasing on the interval [0,3], and how you know.

To tell if a function is increasing or decreasing, we need to see where its derivative is positive and negative. Wherever the derivative is negative, the function will be decreasing, and vice versa.

So, let' find g'(x)

Recall that the derivative of  is just . Also, any exponent term can be derived by multiplying the term by its exponent and then decreasing the exponent by 1.

So, we get:

Next, plug in the endpoints of our function and see what we get for a sign:

Positive, so we are increasing at 0

So our endpoints both yield a positive derivative. If we tested any point between them, we would also get a positive derivative.

This means that our function is increasing on the interval [0,3], because our first derivative is positive.

Example Question #42 : Intervals

Is the function g(x) increasing or decreasing on the interval ?

Possible Answers:

Decreasing, because g'(x) is negative on the interval .

Increasing, because g'(x) is negative on the interval .

Increasing, because g'(x) is positive on the interval .

Decreasing, because g'(x) is positive on the interval .

Correct answer:

Increasing, because g'(x) is positive on the interval .

Explanation:

Is the function g(x) increasing or decreasing on the interval ?

To tell if a function is increasing or decreasing, we need to see if its first derivative is positive or negative. let's find g'(x)

Recall that the derivative of a polynomial can be found by taking each term, multiplying by its exponent and then decreasing the exponent by 1.

Next, we need to see if the function is positive or negative over the given interval.

Begin by finding g'(5)

So, g'(5) is positive. Furthermore, any number greater than 5 will also be positive. This means our function is increasing on the given interval

Increasing, because g'(x) is positive on the interval .

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