Identifying Points of Inflection for a Polynomial Function

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In summary, the conversation discusses finding the points of inflection of a function, which are where the function changes concavity. The suggested method is to find the second derivative of the function and set it equal to zero, and then test points on either side to determine if the function is concave up or down. The conversation also mentions critical numbers and the fact that points of inflection are related to second derivatives.
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hcarter50
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Homework Statement



Find the points of inflection of the graph of the function. (If an answer does not exist, enter DNE.)

Homework Equations


f(x)=1/3x^4 + 4x^3


The Attempt at a Solution


Found f'(x)= x^2(4/3x+12)
Also found critical numbers to x=0 and x=-9

I don't know how to get point of inflection
 
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  • #2
Points of inflection are where the function changes concavity. They are related to second derivatives, aren't they? Look it up.
 
  • #3
For inflection points:
Find the second derivative of the function and set it equal to zero.

I found that that x=-6 and x=0.

Test some points right and left of the second derivative zeros (^) to confirm concave up or concave down. A positive value is concave up, vice versa :)
 

1. What is a point of inflection?

A point of inflection is a point on a curve or function where the curvature changes from concave to convex or vice versa. It is a point where the second derivative of the function is equal to zero, and the sign of the second derivative changes.

2. Why is it important to find points of inflection?

Finding points of inflection can help in understanding the behavior of a curve or function. It can also aid in identifying key features such as maximum or minimum values, and can be useful in optimization problems.

3. How do you find points of inflection?

To find points of inflection, you need to take the second derivative of the function and set it equal to zero. Solve for the variable to get the x-coordinate of the point of inflection. Then, substitute this value into the original function to get the y-coordinate.

4. Can there be more than one point of inflection on a curve?

Yes, there can be multiple points of inflection on a curve. This occurs when the curvature changes multiple times, resulting in multiple points where the second derivative is equal to zero.

5. Are points of inflection always visible on a graph?

No, points of inflection may not always be visible on a graph. Depending on the scale and resolution of the graph, the point of inflection may appear as a sharp turn rather than a flat point. It is important to use the algebraic method to confirm the existence of a point of inflection.

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