Calculus AB : Calculus AB

Study concepts, example questions & explanations for Calculus AB

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Example Questions

Example Question #1 : Differentiate Inverse Functions

Let . Find .

Possible Answers:

Correct answer:

Explanation:

To find the derivative of the inverse of , it is useful to first solve for .

This will help because is needed in the derivative equation, .

Next, the equation for the derivative of an inverse function can be evaluated.

After substituting in for , the derivative of , or , is applied:

Therefore, the correct answer is 

Example Question #2 : Differentiate Inverse Functions

Suppose the points in the table below represent the continuous function . The differentiable function  is the inverse of the function . Find .

Q9 table

Possible Answers:

Correct answer:

Explanation:

Below is the equation for the derivative of :

So, the value of must first be found.

Using the data from the table,  since .

Next, from the table the following can be obtained: 

Now, the appropriate substitutions can be made to solve for .

Example Question #1 : Differentiate Inverse Functions

Find  given .

Possible Answers:

Correct answer:

Explanation:

To find the derivative of the inverse of , it is useful to first solve for .

This will help because  is needed in the derivative equation,  .

Next, the equation for the derivative of an inverse function can be evaluated.

After substituting in  for , the derivative of , or , is found by taking the derivative of  and applying chain rule.

After finding the general term , evaluate at .

Therefore, the correct answer is .

Example Question #1 : Calculate Higher Order Derivatives

If

and ,

then find .

Possible Answers:

Correct answer:

Explanation:

We see the answer is  when we use the product rule.

h(x)=\frac{f+g}{f}

h'(x)=\frac{(f'(x)+g'(x))(f(x))-(f(x)+g(x))(f'(x))}{f^{2}}

h'(x)=\frac{(2+4)(1)-(1+3)(2)}{1^{2}} =-2

Example Question #2 : Calculate Higher Order Derivatives

On a closed interval, the function  is decreasing. What can we say about  and  on these intervals?

Possible Answers:

 is negative

 is decreasing

 is decreasing

 is negative

Two or more of the other answers are correct.

Correct answer:

 is negative

Explanation:

If  is decreasing, then its derivative is negative. The derivative of  is , so this is telling us that  is negative.

For  to be decreasing,  would have to be negative, which we don't know.

 being negative has nothing to do with its slope. 

For  to be decreasing, its derivative  would need to be negative, or, alternatively  would have to be concave down, which we don't know.

Thus, the only correct answer is that  is negative.

Example Question #3 : Calculate Higher Order Derivatives

On what intervals is the function  both concave up and decreasing?

Possible Answers:

Correct answer:

Explanation:

The question is asking when the derivative is negative and the second derivative is positive. First, taking the derivative, we get

Solving for the zero's, we see  hits zero at  and . Constructing an interval test,

, we want to know the sign's in each of these intervals. Thus, we pick a value in each of the intervals and plug it into the derivative to see if it's negative or positive. We've chosen -5, 0, and 1 to be our three values.

Thus, we can see that the derivative is only negative on the interval .

Repeating the process for the second derivative,

The reader can verify that this equation hits 0 at -4/3. Thus, the intervals to test for the second derivative are 

.  Plugging in -2 and 0, we can see that the first interval is negative and the second is positive.

Because we want the interval where the second derivative is positive and the first derivative is negative, we need to take the intersection or overlap of the two intervals we got:

 

If this step is confusing, try drawing it out on a number line -- the first interval is from -3 to 1/3, the second from -4/3 to infinity. They only overlap on the smaller interval of -4/3 to 1/3.

Thus, our final answer is .

Example Question #1 : Calculate Higher Order Derivatives

What does the second derivative of a function tell us?

Possible Answers:

The sign of the second derivative tells us if the function is concave up or down

The sign of the second derivative tells us if the first derivative is increasing or decreasing

All of the above are true

The sign of the second derivative tells us if the function is increasing or decreasing

Correct answer:

All of the above are true

Explanation:

The second derivative is essentially a derivative of the first derivative.  Information we get from the first derivative is, if the first derivative is increasing, then the function is also increasing and concave up.  If the second derivative has a positive sign, then the first derivative is increasing and the function is concave up.  Similarly if the function is concave down, the first derivative is decreasing, and the second derivative is negative.

Example Question #2 : Calculate Higher Order Derivatives

What is the second derivative of .

Possible Answers:

Correct answer:

Explanation:

To find the second derivative we must first find the first derivative.

 

 

Now that we have found the first derivative we will take the derivative of it.

 


And so the second derivative is 

Example Question #1 : Calculate Higher Order Derivatives

When considering a moving object, the second derivative is the ________ .

Possible Answers:

acceleration

distance

None of the above

velocity

Correct answer:

acceleration

Explanation:

If we think about the original function, this tells us the distance.  We take the derivative of the position (we are finding the rate of change of the position) and we have the velocity.  The rate of change of positions, gives us velocity.  We would know which direction we are moving in.  And now, to find the second derivative, we take the derivative of the velocity (finding the rate of change of the velocity) and we are left with the acceleration.  Finding the rate of change of the velocity will tell us at what magnitude we are moving at.

Example Question #4 : Calculate Higher Order Derivatives

Find the second derivative of .

Possible Answers:

Correct answer:

Explanation:

We begin by finding the first derivative.

 

 

Now we will take the derivative of the first derivative.

 

 

 

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