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Homework Help: Need help doing simple re-arrangement

  1. Jun 13, 2010 #1
    1. The problem statement, all variables and given/known data

    How do you go from:


    and rearrange to get:


    My book goes directly from 1 to the other before doing the integration and both are the same, but can someone explain how this rearrangement is done?

  2. jcsd
  3. Jun 13, 2010 #2

    Doc Al

    User Avatar

    Staff: Mentor

    You can (almost) always replace 1 by (anything)/(anything). In this case they used 1 = (2x+1)/(2x+1).
  4. Jun 13, 2010 #3
    They used little trick:
  5. Jun 13, 2010 #4
    Sorry haha but im still confused as to what you did exactly.
  6. Jun 13, 2010 #5
    The first step is that 2x = (2x + 1) - 1

    \frac{(2x+1)-1}{2x+1}= \frac{2x+1}{2x+1} - \frac{1}{2x+1} = 1-\frac{1}{2x+1}

    since [tex]
    \frac{2x+1}{2x+1} = 1
  7. Jun 13, 2010 #6
    so what about this one:


    I dont understand if you are just bringing the bottom up, or how 2x = (2x + 1) - 1
  8. Jun 13, 2010 #7
    Okay nevermind, I see what you are doing. Didnt make sense at first, thank you for the help.
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