Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

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:

    (2x)/(2x+1)

    and rearrange to get:

    1-[(1)/(2x+1)]?

    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?

    Thanks!
     
  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:
    [tex]\frac{2x}{2x+1}=\frac{(2x+1)-1}{2x+1}=1-\frac{1}{2x+1}[/tex]
    :smile:
     
  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

    [tex]
    \frac{(2x+1)-1}{2x+1}= \frac{2x+1}{2x+1} - \frac{1}{2x+1} = 1-\frac{1}{2x+1}
    [/tex]


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


    (3x)/(4x+1)

    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.
     
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook