Results 1 to 7 of 7

Math Help - Series sum question, is this correct?

  1. #1
    Member
    Joined
    Feb 2009
    Posts
    130

    Series sum question, is this correct?

    Hi everyone

    Follow Math Help Forum on Facebook and Google+

  2. #2
    Member
    Joined
    Nov 2009
    Posts
    202
    where is your question????
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Member
    Joined
    Feb 2009
    Posts
    130
    hi everyone,

    sorry,the typo got missing.

    question
    Compute S5 for the following:
    an(limit infinity, n=2) if an=(-1)^n +n^n

    my working:

    n=2,
    -1^2 +2^2 = 5
    n=3
    -1^3+3^3=26
    n=4
    -1^4+4^4= 257
    n=5
    -1^5+5^5=3124
    n=6
    -1^6+6^6=46657
    ans:5+26+257+3124+46657=50069

    is it correct?thank you for helping
    Follow Math Help Forum on Facebook and Google+

  4. #4
    MHF Contributor

    Joined
    Apr 2005
    Posts
    15,393
    Thanks
    1327
    Quote Originally Posted by anderson View Post
    hi everyone,

    sorry,the typo got missing.

    question
    Compute S5 for the following:
    an(limit infinity, n=2) if an=(-1)^n +n^n
    What does "(lim infinity, n=2)" mean? If you are asking about the limit as n goes to infinity, it does not exist. This sequence does not converge.

    my working:

    n=2,
    -1^2 +2^2 = 5
    n=3
    -1^3+3^3=26
    n=4
    -1^4+4^4= 257
    n=5
    -1^5+5^5=3124
    n=6
    -1^6+6^6=46657
    ans:5+26+257+3124+46657=50069

    is it correct?thank you for helping
    Yes, those calculations are correct. And it should be easy now to see that the sequence is unbounded and does not converge to any finite limit.
    Follow Math Help Forum on Facebook and Google+

  5. #5
    Member
    Joined
    Feb 2009
    Posts
    130
    thank you so much for guiding, i couldn't write it out with symbols cos there is no typo.
    i guess i should have wrote limit=infinity, n=2.

    am just wondering,is it possible to use the formula =n/2(2a+(n-1)d) to get the answer.i cant find the common ratio.need some opinion on this.

    thank you for helping.really appreciate your help & advise.
    Follow Math Help Forum on Facebook and Google+

  6. #6
    MHF Contributor

    Joined
    Apr 2005
    Posts
    15,393
    Thanks
    1327
    I finally realized that the "S5" is the "fifth partial sum"! Assuming that is true, then, yes, your answer is correct.

    There is no "common ratio", this is not a geometric series. And the infinite series does not converge.
    Follow Math Help Forum on Facebook and Google+

  7. #7
    Member
    Joined
    Feb 2009
    Posts
    130
    sorry, now i am familiar with latex code..

    compute S_5 for \sum_{n=1}^{infinity} a_n if
    a_n= (-1)^{n}+ n^{n}

    this is the actual question.thank you so much for helping & guiding.
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Power series solution - are these Recurrence relationships correct?
    Posted in the Differential Equations Forum
    Replies: 5
    Last Post: July 17th 2011, 08:06 AM
  2. Replies: 1
    Last Post: May 28th 2011, 01:21 PM
  3. Replies: 1
    Last Post: June 1st 2010, 03:17 AM
  4. Taylor series, is this correct?
    Posted in the Calculus Forum
    Replies: 3
    Last Post: December 4th 2009, 07:20 AM
  5. Testing a series for convergence - is my solution correct?
    Posted in the Differential Geometry Forum
    Replies: 3
    Last Post: September 7th 2009, 03:03 AM

Search Tags


/mathhelpforum @mathhelpforum