Results 1 to 5 of 5

Math Help - sum of series

  1. #1
    Newbie
    Joined
    May 2010
    Posts
    11

    sum of series

    hey guys I'm not sure if this is the right place to post or is it analysis?
    anyways, what is the sum of

    Sum (-1)^n / (n^(1/3) - 0.5) ? from 1 to infinity

    I have tried using the alternating test
    the sequence, 1 / (n^(1/3) - 0.5) is decreasing and tends to 0 right?
    but I tried on mathematica and it says the series does not converge?
    Follow Math Help Forum on Facebook and Google+

  2. #2
    Flow Master
    mr fantastic's Avatar
    Joined
    Dec 2007
    From
    Zeitgeist
    Posts
    16,948
    Thanks
    5
    Quote Originally Posted by godai View Post
    hey guys I'm not sure if this is the right place to post or is it analysis?
    anyways, what is the sum of

    Sum (-1)^n / (n^(1/3) - 0.5) ? from 1 to infinity

    I have tried using the alternating test
    the sequence, 1 / (n^(1/3) - 0.5) is decreasing and tends to 0 right?
    but I tried on mathematica and it says the series does not converge?
    Since the answer given to you by Mathematica is wrong, you must have incorrectly typed the input.

    By the way, why did you ask "What is the sum" ....? Determining whether or not the series converges is NOT the same thing as finding the sum of the series.
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Newbie
    Joined
    May 2010
    Posts
    11
    oops what I meant was does the series converge or not? ><
    Follow Math Help Forum on Facebook and Google+

  4. #4
    MHF Contributor Unknown008's Avatar
    Joined
    May 2010
    From
    Mauritius
    Posts
    1,260
    The series should be converging to 0.

    As n increases, the numerator will either be -1 or 1. So, let's see what happens to the denominator. As n increases, n^(1/3) will also increase. So, the denominator will increase as n increases. At n = infinity, 1/infinity tends to 0, and so does -1/infinity.
    Follow Math Help Forum on Facebook and Google+

  5. #5
    Math Engineering Student
    Krizalid's Avatar
    Joined
    Mar 2007
    From
    Santiago, Chile
    Posts
    3,654
    Thanks
    14
    i think you mean the general term, finding its sum could be hard!
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Replies: 5
    Last Post: October 3rd 2011, 02:12 AM
  2. Replies: 3
    Last Post: September 29th 2010, 07:11 AM
  3. Replies: 0
    Last Post: January 26th 2010, 09:06 AM
  4. Replies: 1
    Last Post: May 5th 2008, 10:44 PM
  5. Replies: 11
    Last Post: April 1st 2008, 01:06 PM

Search Tags


/mathhelpforum @mathhelpforum