Identifying Points of Inflection for a Polynomial Function

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SUMMARY

The discussion focuses on identifying points of inflection for the polynomial function f(x) = (1/3)x^4 + 4x^3. The first derivative, f'(x) = x^2(4/3x + 12), yields critical numbers at x = 0 and x = -9. The second derivative is essential for determining points of inflection, which occur at x = -6 and x = 0. Testing values around these points confirms changes in concavity, indicating the presence of inflection points.

PREREQUISITES
  • Understanding of polynomial functions and their derivatives
  • Knowledge of first and second derivatives
  • Familiarity with concavity and its implications
  • Ability to perform sign tests on intervals
NEXT STEPS
  • Learn how to calculate second derivatives for polynomial functions
  • Study the relationship between concavity and inflection points
  • Explore the application of the first and second derivative tests in calculus
  • Practice identifying inflection points with various polynomial functions
USEFUL FOR

Students studying calculus, particularly those focusing on polynomial functions and their properties, as well as educators teaching derivative concepts.

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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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Points of inflection are where the function changes concavity. They are related to second derivatives, aren't they? Look it up.
 
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 :)
 

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