Confusing Integral!

  • Thread starter acedeno
  • Start date
  • #1
36
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Homework Statement



int[x/((L/2)+d-x)^2] * the integral of x over [(L over 2 + d - x) all squared]*


Homework Equations


Integral chart



The Attempt at a Solution


I have done this so many ways with so many different answers. Could somebody who is without a doubt sure of the answer please respond because this integral is driving me INSANE!
 

Answers and Replies

  • #2
2,967
5
You can't have x in the upper limit and as an integration dummy variable.
 
  • #3
36
2
Not following.
 
  • #4
2,967
5
Your dummy variable is x, your upper limit contains x.
 
  • #5
SammyS
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Not following.
Is this the integral?

[itex]\displaystyle \int\frac{x}{((L/2)+d-x)^2}\ dx[/itex]
 
  • #6
36
2
Is this the integral?

[itex]\displaystyle \int\frac{x}{((L/2)+d-x)^2}\ dx[/itex]
Yes, that is the integral.
 
  • #7
SammyS
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To simplify things, Let A = (L/2) + d .

Your integral becomes: [itex]\displaystyle \int\frac{x}{(A-x)^2}\ dx[/itex]

Notice the (A - x)2 = (x - A)2.

Use the substitution: u = x - A .
 
  • #8
2,967
5
No, use the substitution:

[tex]
u = (x - A)^{2}
[/tex]
 
  • #9
2,571
1
No, use the substitution:

[tex]
u = (x - A)^{2}
[/tex]
No unique substitution, but Sammy's substation is easier to work with
 

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