Calculus 1 : Equations

Study concepts, example questions & explanations for Calculus 1

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Example Questions

Example Question #3 : Local Minimum

Find the  coordinate of the local minumum of the following function.

Possible Answers:

None of these

Correct answer:

Explanation:

The local maximums and minumums of a function are where the slope of the line tangent to the function is 0. To find the slope of the tangent line we must find the derivative. Then we must set ot equal to 0 and solve. The derivative of  is 

The critical points are at the above two points. To find the minimum we must plug both back into the origianl function.

Thus the local min is at x=-2.

 

Example Question #1 : How To Find Local Minimum By Graphing Differential Equations

You are given the function . Find the minimum point of the function. 

Possible Answers:

Correct answer:

Explanation:

To find the minimum of a function, start by finding the critical points of that function, or points where the derivative is equal to zero. Use the power rule to find the derivative:

Applying the power rule to the given equation, noting the constants in the first and second terms:

Then check to see if the critical point is a maximum, minimum, or an inflection point by taking the second derivative, using the power rule once again.

Because the second derivative is positive, the critical point  is a minimum.

To find the point where the minimum occurs, plug  back into the original equation and solve for .

Therefore, the minimum is 

Example Question #1 : How To Find Local Minimum By Graphing Differential Equations

A function  is given by the equation 

.

By graphing the derivative of , which  value corresponds to the local minumum?

Possible Answers:

Correct answer:

Explanation:

The local minimum of a function can be found by finding the derivative and graphing it. The point in which the x axis is crossed from below gives the x position where the local minimum is found. Taking the derivative:

The graph of the derivative is shown below:

 

Problem 8

As shown by the graph, the local minimum is found at x = -4.

Example Question #1 : Differential Equations

The function f(x) is shown here in the graph

Problem 10

Without solving for the derivative, which of the following graphs is the graph of the derivative of , i.e the graph of ?

Possible Answers:

Problem 10c

Problem 10b

Problem 10a

None of these graphs could be the derivative of .

Problem 10d

Correct answer:

Problem 10a

Explanation:

In order to determine the graph by inspection, there are key features to look for. The most important is the locations of the local maxima and minima in the graph of f(x). These points correspond to the x-intercepts in the graph of the derivative. Taking a look at the graph of f(x), you can see that the x intercepts on the graph of f'(x) will be located roughly at x = -3 and x = 4.5. Looking at the possible answers, the only two that could be graphs of f'(x) are these two:

Problem 10a and Problem 10c

The next step would then be to see which corresponds correctly to maxima and minima. Since the point at x = -3 is a local maximum, f(x) will increase up until the point at which it is maximum, then begin to drop. As seen in the positively oriented parabola, the rate of change of f(x) (the derivative) is positive up until it reaches x = -3. This means that f(x) was increasing, and indicates that this point was a local maximum. On the other hand, if you look at the graph on the left with the negatively oriented parabola, f'(x) is negative until it reaches the local maximum, which doesn't make sense, since that would mean it was decreasing up until the point and then increasing. This indicates a minima.

Since the point at x = -3 is a local maximum, the only graph that could be the derivative of f(x) is the positively oriented parabola. 

Example Question #1 : How To Find Solutions To Differential Equations

Find the derivative of (5+3x)5.

 

Possible Answers:
5(5+3x)^4
5x(5+3x)^4
15x(5+3x)^4
5(5+3x)^4x
15(5+3x)^4
Correct answer: 15(5+3x)^4
Explanation:

We'll solve this using the chain rule.

Dx[(5+3x)5]

=5(5+3x)4 * Dx[5+3x]

=5(5+3x)4(3)

=15(5+3x)4

Example Question #2 : How To Find Solutions To Differential Equations

Find Dx[sin(7x)].

Possible Answers:
7cos(7x)
-7sin(7x)
7sin(7x)
7sin(7x)cos(7x)
-7cos(7x)
Correct answer: 7cos(7x)
Explanation:

First, remember that Dx[sin(x)]=cos(x). Now we can solve the problem using the Chain Rule.

Dx[sin(7x)]

=cos(7x)*Dx[7x]

=cos(7x)*(7)

=7cos(7x)

Example Question #3 : How To Find Solutions To Differential Equations

Calculate fxxyz if f(x,y,z)=sin(4x+yz).

Possible Answers:
4sin(4x+yz)
cos(4x+yz)
-16cos(4x+yz) +16yzsin(4x+yz)
-16sin(4x+yz)
arctan(4x+yz)
Correct answer: -16cos(4x+yz) +16yzsin(4x+yz)
Explanation:

We can calculate this answer in steps.  We start with differentiating in terms of the left most variable in "xxyz".  So here we start by taking the derivative with respect to x. 

First, fx= 4cos(4x+yz)

Then, fxx= -16sin(4x+yz)

fxxy= -16zcos(4x+yz)

Finally, fxxyz= -16cos(4x+yz) + 16yzsin(4x+yz) 

Example Question #1 : How To Find Solutions To Differential Equations

Integrate 

Possible Answers:

Correct answer:

Explanation:

 thus: 


Example Question #2 : How To Find Solutions To Differential Equations

Integrate :

Possible Answers:

Correct answer:

Explanation:

thus:

Example Question #3 : How To Find Solutions To Differential Equations

Find the general solution, , to the differential equation

 .

Possible Answers:

Correct answer:

Explanation:

We can use separation of variables to solve this problem since all of the "y-terms" are on one side and all of the "x-terms" are on the other side.  The equation can be written as .  

Integrating both sides gives us 

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