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Average value for integrals

  • Thread starter Jbreezy
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  • #1
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Homework Statement


I have a question can the average value for an integral be negative. I don't see why not just checking.


You know this evalutation f_ave = (1/b-a) ∫ f(x) dx


Homework Equations



thx

The Attempt at a Solution

 

Answers and Replies

  • #2
pasmith
Homework Helper
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Homework Statement


I have a question can the average value for an integral be negative.

You know this evalutation f_ave = (1/b-a) ∫ f(x) dx
That is the average value of the function f on [a,b]. It can of course be negative, and will be if f(x) < 0 for all x in [a,b].
 
  • #3
HallsofIvy
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Homework Helper
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Homework Statement


I have a question can the average value for an integral be negative. I don't see why not just checking.
If the average value of the function is negative, of course!

You know this evalutation f_ave = (1/b-a) ∫ f(x) dx
More correctly f_ave = (1/(b-a)) ∫ f(x) dx. What you wrote would normally be interpreted
f_ave = ((1/b)-a) ∫ f(x) dx


Homework Equations



thxx

The Attempt at a Solution

Of course. Take the simplest example: f(x)= -1 for all x.
Then [tex]\int_0^1 f(x)dx= -\int_0^1 dx= -(1- 0)= -1[/tex]
Slightly more complicated, if f(x)= -x,
[tex]\int_0^1 f(x)dx= -\int_0^1 xdx= -\frac{1}{2}[/tex].
 

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