Calculus 1 : Graphing Functions

Study concepts, example questions & explanations for Calculus 1

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Example Questions

Example Question #1 : How To Find Relative Maximum On The Interval By Graphing Functions

Given

Find the -coordinate of the relative maximum on the interval .

Possible Answers:

Cannot be determined

Correct answer:

Explanation:

To find relative maximums, we need to find where our first derivative changes sign. To do this, find your first derivative and then find where it is equal to zero.

Begin with:

    at 

This means we have extrema at x=0 and x=-8/3

Because we are only concerned about the interval from -5 to 0, we only need to test points on that interval. Try points between our two extrema, as well as one between -8/3 and -5.

So our first derivative goes from negative to positive at -8/3, thus this is the x coordinate of our relative maximum on this interval.

Example Question #2 : How To Find Relative Maximum On The Interval By Graphing Functions

Where is the maximum value of the function 

on the interval  ?

Possible Answers:

 

Correct answer:

Explanation:

Though there are relative maxima at  and  (found by setting the first derivative of the function equal to zero and solving for x.)  the maximum value along the whole interval is actually at the upper endpoint, when .  When looking for extrema along an interval, looking for zeros of the first derivative does not account for endpoint extrema.

Function

Example Question #1 : How To Find Relative Maximum On The Interval By Graphing Functions

Determine the relative maxima for the function:

Possible Answers:

Correct answer:

Explanation:

To determine the relative maxima for the function, we must determine where the first derivative of the function changes from positive to negative.

The first derivative of the function is

and was found using the following rule:

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

Using the critical values, we can then create the intervals on which we evaluate the sign of the first derivative:

To check the sign of the first derivative, plug in any value on each interval into the first derivative function. On the first interval, the first derivative is positive, on the second, it is negative, and on the third it is positive. The first derivative changes from positive to negative at  so a relative maximum exists here.

Example Question #4 : How To Find Relative Maximum On The Interval By Graphing Functions

Find the local max of 

 

using the equation and/or the following graph.

Graph2

Possible Answers:

Correct answer:

Explanation:

We notice that this function has 2 extrema which are located at  and . We could have also of found this by looking at the function itself: 

.  

We know that extrema exist when the slope of the function is zero, hence we take the derivative, set it equal to zero, and than solve for x.

The derivative is the following: 

.  

Therefore setting both pieces equal to zero we see the following: 

 and .  

Finding out if one of these x values produce a local min or max however requires either the first derivative test, the second derivative test, or analyzing the graph. We see that for a small neighborhood around ,  is the largest term, hence it is a local max.  Similarly, for a small neighborhood around ,  is the smallest term, hence  is a local min.  

Therefore when  is the only spot in which a local max occurs. Remember that it is not the x value that must be the largest, rather it is it's corresponding y value.

Example Question #1 : How To Find Relative Minimum On The Interval By Graphing Functions

The following is a list of values at certain points for continuous . By mean-value theorem, how many zeroes must this function have?

 

Possible Answers:

Exactly 1

At most 2

At least 2

Exactly 2

At least 1

Correct answer:

At least 2

Explanation:

The mean value theorem states that if continuous   has , then for all , there must be an  that maps to , so since the value above go from negative to positive twice, zero must be mapped to at least twice. 

Example Question #2 : How To Find Relative Minimum On The Interval By Graphing Functions

A relative minimum of a function is all the points x, in the domain of the function, such that it is the smallest value for some neighborhood.  These are points in which the first derivative is 0 or it does not exist.  

Find the relative minimum of the function

 

using the following graph and the function.

Graph1

Possible Answers:

Correct answer:

Explanation:

We notice that this function has 2 extrema which are located at x=-1 and x=0.  We could have also of found this by looking at the function itself: 

.  

We know that extrema exist when the slope of the function is zero, hence we take the derivative, set it equal to zero, and than solve for x.

The derivative is the following: 

.  

Therefore setting both pieces equal to zero we see the following: 

 and .  

Finding out if one of these x values produce a local min or max however requires either the first derivative test, the second derivative test, or analyzing the graph. We see that for a small neighborhood around ,  is the largest term, hence it is a local max. Similarly, for a small neighborhood around ,  is the smallest term, hence  is a local min and the only local min of this function. Remember that it is not the x value that must be the smallest, rather it is it's corresponding y value.

Example Question #1 : How To Find Length Of Line By Graphing Functions

Consider a function  with first-derivative:

.

Which integral can calculate the length along this curve between  and ?

 

Possible Answers:

This is not possible with the information given.

Correct answer:

Explanation:

To determine the length of a curve between two points, we evaluate the integral

There are many reasons this works, but we'll give an informal explanation here:Canvas2

If we divide this curve into three line-segments, we can see that they become more and more similar to the original curve. By adding up all the little hypotenuses, we can arrive at the length of the curve. Note, that

If we think of the integration symbol as a sum of infinitely small parts, this gets us the formula for length:

.

Returning to the problem, we plug the derivative into the length formula:

substitute:

Simplify:

By trigonometric identities we get:

Example Question #1 : Length Of Line

Find the length of the line segment between points A and B:

 

Possible Answers:

Correct answer:

Explanation:

The distance between two points can be easily found using the Distance Formula:

Applying the points we are given to this formula results in:

This is one of the answer choices.

Example Question #1 : How To Find Equation Of Line By Graphing Functions

What is the equation of the line tangent to f(x) = 4x3 – 2x2 + 4 at x = 5?

Possible Answers:

y = 280x – 946

y = 44x + 245

y = 85x + 24

y = 220x – 550

None of the other answers

Correct answer:

y = 280x – 946

Explanation:

First, take the derivative of f(x). This is very easy:

f'(x) = 12x2 – 4x

Now, the slope of the tangent line at x = 5 is f'(5). Evaluated, this is: f'(5) = 12 * 5 * 5 – 4 * 5 = 300 – 20 = 280

Now, we must find the intersection point on the original line:

f(5) = 4 * 53 – 2 * 52 + 4 = 500 – 50 + 4 = 454

Therefore, the point of tangent intersection is (5,454).

Using the point-slope form of linear equations, we can find the line:

(y – 454) = 280(x – 5)

y – 454 = 280x – 1400

y = 280x – 946

Example Question #221 : Graphing Functions

Find the equation of the line tangent to  at the point .

Possible Answers:

Correct answer:

Explanation:

The equation of the tangent line will have the form , where  is the slope of the line and .  

To find the slope, we need to evaluate the derivative at :

 

Now that we have the slope, we can determine the equation of the tangent line using the point-slope formula:

 

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