Results 1 to 3 of 3

Math Help - Finding sumfunctions for power series

  1. #1
    Member
    Joined
    May 2010
    Posts
    98

    Finding sumfunctions for power series

    Hello

    I need to find the sumfunction and the radius of convergence + convergence range for the following:

    \sum_{n=0}^{\infty} (2n+1)(x+7)^n

    What i did was this:

    \lim_{n\rightarrow\infty} \frac{2n+1}{2(n+1)+1}=\lim_{n\rightarrow\infty} \frac{2n+1}{2(n+3)} which converges to 1 for n\rightarrow\infty so radius of convergense is 1, but what is the convergence range?

    Or am i totally off here?
    Follow Math Help Forum on Facebook and Google+

  2. #2
    Math Engineering Student
    Krizalid's Avatar
    Joined
    Mar 2007
    From
    Santiago, Chile
    Posts
    3,654
    Thanks
    11
    |x+7|<1, now check the endpoints.
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Member
    Joined
    May 2010
    Posts
    98
    Quote Originally Posted by Krizalid View Post
    |x+7|<1, now check the endpoints.
    Yes thats what i came up with too, but i tried to calc it in maple using:

    Sum((2*n+1)*((x+7)^n), n=0..infinity); simplify(value(%));

    Which gave me \frac{x+8}{(x+6)^2}
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Finding a power series
    Posted in the Calculus Forum
    Replies: 4
    Last Post: November 21st 2011, 01:23 PM
  2. Finding a power series
    Posted in the Calculus Forum
    Replies: 3
    Last Post: March 6th 2010, 07:41 AM
  3. Help finding a power series
    Posted in the Calculus Forum
    Replies: 2
    Last Post: September 29th 2008, 04:26 PM
  4. Power series sumfunctions
    Posted in the Calculus Forum
    Replies: 0
    Last Post: June 19th 2008, 02:05 PM
  5. Replies: 10
    Last Post: April 18th 2008, 10:35 PM

Search Tags


/mathhelpforum @mathhelpforum