Calculus 1 : How to graph functions of points of inflection

Study concepts, example questions & explanations for Calculus 1

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Example Questions

Example Question #11 : Points Of Inflection

Which of the following is a point of inflection on ?

Possible Answers:

Correct answer:

Explanation:

Which of the following is a point of inflection on f(x)?

To find points of inflection, we need to find where the second derivative is 0.

So, find f''(x)

So, we have a point of inflection at x=0.

Find f(0) to find the y-coordinate:

So our point is at .

Example Question #4 : Inflection Points

Which of the following is a point of inflection of  on the interval ?

Possible Answers:

Correct answer:

Explanation:

Which of the following is a point of inflection of f(x) on the interval ?

To find points of inflection, we need to know where the second derivative of the function is equal to zero. So, find the second derivative:

So, where on the given interval does ?

Well, we know from our unit circle that ,

So we would have a point of inflection at , but we still need to find the y-coordinate of our POI. find this by finding 

So our POI is:

 

Example Question #5 : Inflection Points

Which of the following functions has an inflection point where concavity changes?

Possible Answers:

Correct answer:

Explanation:

For a graph to have an inflection point, the second derivative must be equal to zero. We also want the concavity to change at that point. 

, for all real numbers, but this is a line and has no concavity associated with it, so not this one.

, there are no real values of  for which this equals zero, so no inflection points.

 

, same story here.

 

, so no inflection points here.

 

This leaves us with 

, whose derivatives are a bit more difficult to take.

 

, so by the chain rule we get

So,  when . So 

.  This is our correct answer.

Example Question #12 : Points Of Inflection

Find the inflection point of this 3rd degree polynomial:

 

Possible Answers:

Correct answer:

Explanation:

To find the inflection point we must find where the second derivative of a function is 0.

Calculating the second derivative is fairly simple. We just need to know that :

The first derivative is 

 

and if we take the derivative once more we get 

.

Setting this equal to zero, we get 

And now all we have to do is plug this value, 3/5, into our original polynomial, to get the answer.

Example Question #13 : Points Of Inflection

Determine the point(s) of inflection for the function .

Possible Answers:

only

only

only

This function has no points of inflection.

and

Correct answer:

only

Explanation:

Points of inflection occur when the second derivative changes signs.

The second derivative equals zero at and . However, the factor  has degree two in the second derivative.  This indicates that is a root of the second derivative with multiplicity two, so the second derivative does not change signs at this value.  It only changes signs at .  Since , the point of inflection is .

Example Question #14 : Points Of Inflection

Determine the number of points of inflection found in the funtion .

Possible Answers:

Correct answer:

Explanation:

To find the inflection points of a function we need to take the second derivative and find which values make it zero.

To find the first and second derivative we will need to apply the power rule, .

Given, 

and applying the power rule we get,

.

Points of inflection happen when the second derivative changes signs.  The quadratic above changes signs at and

This can be determined by factoring,

,

or by the quadratic formula,

.

Example Question #15 : Points Of Inflection

Find the point of inflection of the function .

Possible Answers:

There is no inflection point.

Correct answer:

Explanation:

The point of inflection can be found by setting the second derivative equal to 0.

The power rule is given by:

Use the power rule twice to find the second derivative.

Set the second derivative equal to  and solve for .

Find the point of inflection by plugging  back into the original equation.

Therefore, the point of inflection is 

Example Question #2571 : Calculus

Find the x-values for the points of inflection of the following function:

Possible Answers:

The points of inflection are imaginary numbers

Correct answer:

Explanation:

To find where the points of inflection occur, we must find the points at which the second derivative changes sign. 

First, we must find the second derivative:

The derivatives were found using the following rule:

Next, we must find the x values at which the second derivative is equal to zero:

Now, we make the intervals on which we will examine the sign of the second derivative, using the above x value:

Note that at the bounds of the intervals the second derivative is neither positive nor negative.

On the first interval, the second derivative is negative, while on the second, the second derivative is positive. (We check the sign of the second derivative by plugging in any value on the interval into the second derivative function.) A sign change occured at , so this is our answer. 

Example Question #2572 : Calculus

Where does the function  have a point of inflection?

Possible Answers:

Correct answer:

Explanation:

The point of inflection of an object can be found by setting the second derivative of the function equal to zero and solving. 

Example Question #2573 : Calculus

Find the  value of the point of inflection of the function .

Possible Answers:

Correct answer:

Explanation:

First, we need to simplify the expression.  Sine the numerator has more terms than the denominator, we can simply divide out both terms.  

.

Now, we must compute the second derivative of this function, and set it equal to zero. 

.

.

.

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