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Homework Help: Bah. Where did the -1 come from?

  1. Nov 19, 2008 #1
    http://img48.imageshack.us/img48/6110/qnisstb4.jpg [Broken]

    I always get the positive and negatives confused. I don't have a teacher to guide me so help would be appreciated. The correct answer is in green ink.

    Thanks
     
    Last edited by a moderator: May 3, 2017
  2. jcsd
  3. Nov 19, 2008 #2

    HallsofIvy

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    Science Advisor

    At one point you have converted 1/(x+2) into (-1)/(2- x). That's wrong. That would be equal to 1/(x-2) not 1/(x+ 2). What you want, rather, is 1/(x+ 2)= 1/(2+x)= 1/(2-(-x)). Then dividing by numerator and denominator by 2: (1/2)/(1-(-x/2)). The "r" in your geometric series is -x/2, not x/2.
     
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