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Find all values of x in which the series converges

  1. Mar 25, 2012 #1
    1. The problem statement, all variables and given/known data
    Find all values of x for which the series Ʃ (4x+5)^n/2^n converges. (n=0; n→∞)
    Answer choices: (3/4,-3/4)
    (3/4,7/4)
    (-7/4,7/4)
    (-5/4,5/4)
    (-7/4,-3/4)



    2. Relevant equations




    3. The attempt at a solution
    I think the answer is -7/4,-3/4. If I remember correctly, there is a test that states that a series converges if the limit goes to 0. Is this correct?
     
  2. jcsd
  3. Mar 25, 2012 #2

    tiny-tim

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    Science Advisor
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    hi turbokaz! :smile:

    (yes, correct answer)

    look at it this way …

    it's ∑ an where a = (4x+5)/2

    so what is the equation for when ∑ an converges? :wink:
     
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