Are there inflection points in the function f(x) = x ln(x)?

  • Thread starter Thread starter Greywolfe1982
  • Start date Start date
  • Tags Tags
    Points
Click For Summary

Homework Help Overview

The discussion revolves around identifying inflection points for the function f(x) = x ln(x). The original poster expresses uncertainty about the function's behavior, particularly regarding its concavity and the implications of its domain.

Discussion Character

  • Conceptual clarification, Assumption checking

Approaches and Questions Raised

  • The original poster questions the existence of inflection points and the concavity of the function, noting a discrepancy with WolframAlpha's output for x <= 0. Other participants provide links to WolframAlpha, suggesting further exploration of the function's properties.

Discussion Status

The discussion is ongoing, with participants exploring the implications of the function's behavior for negative values of x. There is a recognition of the function's complex nature when x < 0, but no consensus has been reached regarding the original poster's concerns.

Contextual Notes

Participants are considering the implications of the function's domain and the behavior of logarithmic functions with negative inputs, which may affect their understanding of inflection points.

Greywolfe1982
Messages
60
Reaction score
0
Finding inflection points of x(ln(x)) (or "Why is WolframAlpha telling me this?")

The question is finding the points of inflection for f(x)=xlnx. As far as I know, it has none, and is concave up for the entire function within its domain, x>0. When I look at the graph on WolframAlpha though, it's telling me there's a real part to the function for x<=0. Would somebody care to explain what I'm missing? Or is it a glitch on WolframAlpha's part?

Here's the output:
http://www.wolframalpha.com/input/?i=x(lnx)
 
Physics news on Phys.org


It's a complex number. Therefore it has real and imaginary parts when x&lt;0.
 

Similar threads

Replies
1
Views
1K
Replies
7
Views
2K
Replies
11
Views
2K
  • · Replies 4 ·
Replies
4
Views
3K
Replies
5
Views
2K
  • · Replies 34 ·
2
Replies
34
Views
4K
  • · Replies 2 ·
Replies
2
Views
2K
  • · Replies 18 ·
Replies
18
Views
2K
  • · Replies 4 ·
Replies
4
Views
2K
  • · Replies 9 ·
Replies
9
Views
3K