How to Find Extrema, Roots, Inflection Points, and Concavity Using Derivatives?

  • Thread starter Thread starter crybllrd
  • Start date Start date
  • Tags Tags
    Derivative
Click For Summary
SUMMARY

The discussion focuses on finding extrema, roots, inflection points, and concavity for the function y=3(x-1)^{\frac{1}{3}}-(x-1)^{2} using first and second derivative tests. The first derivative, y' = 2(x-1)^{-\frac{1}{3}} - 2(x-1), was simplified incorrectly, leading to confusion about the location of extrema at x=0 and x=2. A correction was noted regarding the derivative of the first term, which should be d/dx(3(x - 1)^{1/3}) = (x - 1)^{-\frac{2}{3}}. The sharp turn at (1,0) indicates a point of interest for further analysis.

PREREQUISITES
  • Understanding of calculus concepts such as derivatives and their applications.
  • Familiarity with the first and second derivative tests for determining extrema and concavity.
  • Knowledge of algebraic simplification techniques.
  • Ability to interpret graphical representations of functions.
NEXT STEPS
  • Review the process of finding critical points using first derivatives.
  • Study the application of the second derivative test for concavity and inflection points.
  • Practice simplifying complex derivatives, particularly involving fractional exponents.
  • Explore graphing techniques to visualize functions and their behavior at critical points.
USEFUL FOR

Students studying calculus, particularly those learning about derivatives and their applications in finding extrema and concavity. This discussion is beneficial for anyone needing clarification on derivative simplification and critical point analysis.

crybllrd
Messages
120
Reaction score
0

Homework Statement



[itex]y=3(x-1)^{\frac{1}{3}}-(x-1)^{2}[/itex]

I need to find all extrema, roots, inflection points, and concavity using first and second derivative tests.
I usually do not have a problem with these, but I need to find some extrema that I know exist.

The Attempt at a Solution



[itex]y'=2(x-1)^{\frac{-1}{3}}-2(x-1)[/itex]

simplified to:

[itex]y'=\frac{2+(-2x+2)(x-1)^{\frac{1}{3}}}{(x-1)^{\frac{1}{3}}}[/itex]

From looking at a graph I can see that there are extrema at x=0, and x=2. There is also a sharp turn at (1,0). However, i am not seeing these extrema in my first derivative. Did I not simplify enough or make an algebraic error?
 
Physics news on Phys.org
crybllrd said:

Homework Statement



[itex]y=3(x-1)^{\frac{1}{3}}-(x-1)^{2}[/itex]

I need to find all extrema, roots, inflection points, and concavity using first and second derivative tests.
I usually do not have a problem with these, but I need to find some extrema that I know exist.

The Attempt at a Solution



[itex]y'=2(x-1)^{\frac{-1}{3}}-2(x-1)[/itex]
There's a mistake in the above.
d/dx(3(x - 1)^(1/3)) = (x - 1)^(-2/3)
crybllrd said:
simplified to:

[itex]y'=\frac{2+(-2x+2)(x-1)^{\frac{1}{3}}}{(x-1)^{\frac{1}{3}}}[/itex]

From looking at a graph I can see that there are extrema at x=0, and x=2. There is also a sharp turn at (1,0). However, i am not seeing these extrema in my first derivative. Did I not simplify enough or make an algebraic error?
 
Thanks, I'm not sure how I missed that. I can take it from here.
Thanks again
 

Similar threads

Replies
11
Views
2K
Replies
1
Views
1K
Replies
7
Views
2K
  • · Replies 4 ·
Replies
4
Views
3K
Replies
5
Views
2K
Replies
7
Views
2K
  • · Replies 6 ·
Replies
6
Views
2K
  • · Replies 2 ·
Replies
2
Views
2K
Replies
22
Views
3K
Replies
2
Views
2K