What is the critical point of xe^x?

In summary, the conversation discusses the critical point of xe^x and the definition of a critical point. The critical point for this function is at x = -1, where its derivative is equal to 0. There is some confusion about the value of y= xex when x=1, as it is not an asymptote and has a value of 1. The conversation also mentions the use of calculators and how they can complicate seemingly simple problems.
  • #1
Mitchtwitchita
190
0
can anybody tell me what the critical point of xe^x is? When I try putting it into my calculator, it just shows a line staring at zero with an asymptote at x=1.
 
Mathematics news on Phys.org
  • #2
What is the definition of "critical point"?

And I can't help but wonder what you put into your calculator! y= xex does not have any asymptotes. What is the value of y= xex when x= 1?
 
  • #3
[tex] \frac{\partial}{\partial x} xe^x = x*e^x + e^x[/tex]

so you need to find

[tex] 0 = x*e^x + e^x [/tex]

so the critical point is

[tex] x = -1 [/tex]

it is the place where the function is not locally a diffeomorphism, that is where the inverse function theorem don't apply, so for higher dimensions you need to calculate the jacobian.
 
  • #4
Thanks for your help guys. I think I got it now. When x=1, the answer is -1. This is the critical point for the function. I don't what the deal was with my calculator. It could have been the scale. Anyhoo, thanks again.
 
  • #5
not sure what you meen by:

When x=1, the answer is -1

it is not 'when x=1 or equal to anything then...'

you simply need to find where the derivative is equal to 0 or undefined, and for your function that is in x=-1.
 
  • #6
another argument against calculators. a trivial problem made hard by using and believing a calculator.
 
  • #7
Mitchtwitchita said:
Thanks for your help guys. I think I got it now. When x=1, the answer is -1. This is the critical point for the function. I don't what the deal was with my calculator. It could have been the scale. Anyhoo, thanks again.
Then you don't got it. If "when x= 1, the answer is -1" is in response to my question "What is the value of y= xex when x= 1?" (my point being that if it has a value, x= 1 cannot be an asyptote), then when x= 1, y= xex= 1(e1)= 1. I can't imagine how you would get a negative number for that. And you have already been told that the critical point is NOT at x= 1.
 
  • #8
I apologize, I see that my answer has caused some clamor. I meant that when I differentiated and solved for x, the answer is -1...which was my initial query. Thanks again for the help guys!
 

1. What are critical points?

Critical points are points on a function where the derivative is equal to zero or does not exist. They are important in calculus because they can help determine the maxima, minima, and inflection points of a function.

2. How do you find the critical points of xe^x?

To find the critical points of xe^x, we need to take the derivative of the function, which is e^x + xe^x. Then, we set the derivative equal to zero and solve for x. This gives us the critical point x = -1.

3. What is the significance of critical points in xe^x?

In xe^x, the critical point at x = -1 is the minimum point of the function. This means that at this point, the function has the lowest possible value. It is also the point where the function changes from decreasing to increasing.

4. How do critical points affect the graph of xe^x?

The critical point at x = -1 affects the graph of xe^x by creating a "turning point" on the graph. Before the critical point, the graph is decreasing, and after the critical point, the graph is increasing. The graph also has a concave up shape at the critical point.

5. Are critical points the only points where the derivative is equal to zero?

No, there can be other points where the derivative is equal to zero, but not all of them are critical points. Some may be inflection points or points where the function has a horizontal tangent line. Critical points are specifically points where the function changes from increasing to decreasing or vice versa.

Similar threads

Replies
1
Views
830
Replies
3
Views
2K
  • General Math
Replies
6
Views
890
Replies
5
Views
711
  • General Math
Replies
23
Views
1K
  • Precalculus Mathematics Homework Help
Replies
5
Views
137
Replies
20
Views
1K
Replies
10
Views
1K
Replies
4
Views
610
Back
Top