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Homework Help: U substitution problem

  1. Sep 27, 2012 #1
    1. The problem statement, all variables and given/known data

    ∫3xdx/√(1-2x)

    2. Relevant equations



    3. The attempt at a solution

    so i tried making u=3x which makes du=3dx but that substitution doesn't get rid of the x unde the square root. i tried u=1-2x and that gives du=-2dx and that doesn't get rid of the x on top. So i'm stuck and have no idea what to do here. Please help me out. Thanks!
    1. The problem statement, all variables and given/known data



    2. Relevant equations



    3. The attempt at a solution
     
  2. jcsd
  3. Sep 27, 2012 #2

    Mark44

    Staff: Mentor

    Your second substitution will work if you replace x and dx with the corresponding values of u and du. Note that if u = 1 - 2x, then x = (1/2)(1 - u).
     
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