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Integration Help - u Substiution. [ ]

  1. May 28, 2009 #1
    Integration Help - u Substiution. [urgent]

    1. The problem statement, all variables and given/known data

    Evaluate the following integrals.
    (Here are the functions with respect to x)

    1. x^2/(x+1)^5

    2. (4x^2+4x+1)^10

    3. x^2[sqr(1-x)]

    4. (x+1)(x-3)^10

    5. sqr(x)[sqr(4+xsqr(x))]

    Looking more for how to solve them, not what the answer is..
    Im good when its in the simple form, its just when its not multiplied by the derivative of the inside I get stuck.


    2. Relevant equations



    3. The attempt at a solution
     
    Last edited: May 28, 2009
  2. jcsd
  3. May 28, 2009 #2

    djeitnstine

    User Avatar
    Gold Member

    Re: Integration Help - u Substiution. [urgent]

    For the first one, u = x+1. thus du = dx right? so what is x in the numerator? Just solve for x, nothing special about it to get stuck on =] *hint you get a quadratic in 'u' on top which makes the integral simple.
     
  4. May 28, 2009 #3
    Re: Integration Help - u Substiution. [urgent]

    the second one is just (2x+1)^20
     
  5. May 29, 2009 #4
    Re: Integration Help - u Substiution. [urgent]

    Thank you, and as for the first one, you must multiple the numerator by u^-5
     
  6. May 29, 2009 #5

    Mark44

    Staff: Mentor

    Re: Integration Help - u Substiution. [urgent]

    That doesn't make any sense to me. If you multiply an expression by something, its value changes unless you multiply by 1. Now maybe what you did is valid, but you aren't explaining it very clearly.
     
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