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Finding values of x where the infinite geometric series converge

  1. Nov 4, 2008 #1
    1. The problem statement, all variables and given/known data
    (2+x)+(2+x)^2+(2+x)^3 + ....


    2. Relevant equations





    3. The attempt at a solution

    Ive found that the l r l < 1

    the r of this equation is (2 + x)

    so we have -1 < 2 + x < 1

    The values of x where the series coverges is -3 < x < -1

    Is this correct?

    Thanks!
     
  2. jcsd
  3. Nov 5, 2008 #2

    tiny-tim

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    hmm …

    :rofl: :rofl: :rofl: :rofl:

    Hint: does it converge for x = 0? :wink:
     
  4. Nov 5, 2008 #3

    gabbagabbahey

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    Looks good to me:approve:
     
  5. Nov 7, 2008 #4
    Re: hmm …



    No I dont think so?

    Does your laughing faces mean I got it right? lol
     
  6. Nov 7, 2008 #5

    tiny-tim

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    i need glasses

    oh dear … I read a -1 as a 1. :redface:

    Yes … sorry, meeklobraca … you got it right! :biggrin:
     
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