Results 1 to 3 of 3

Math Help - radius of convergence and interval of convergence of the series

  1. #1
    Junior Member
    Joined
    Oct 2009
    Posts
    72

    radius of convergence and interval of convergence of the series

    \sum_{n=1}^{\infty}  \frac{n}{7^n} (x + 4)^n

    I used the ratio test and after some cancellations, i get

    \sum_{n=1}^{\infty} \frac{n+1}{n} * \frac{x+4}{7}

    not sure if what i got so far is correct but i get stuck after i get to this part.

    How do i finish this problem? thanks!
    Follow Math Help Forum on Facebook and Google+

  2. #2
    Newbie
    Joined
    May 2010
    From
    Scranton, PA
    Posts
    1
    After applying the ratio test, you should get
    \underset{n\rightarrow\infty}{\lim}\frac{n+1}{n}*\  frac{x+4}{7}
    instead of another sigma.

    To find the radius of convergence, you simply have to find the values of x that would make the series converge.
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Junior Member
    Joined
    Oct 2009
    Posts
    72
    ahh silly mistake from me. forgot about that. thanks!
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Replies: 1
    Last Post: December 10th 2009, 03:04 AM
  2. Replies: 3
    Last Post: October 9th 2009, 07:26 AM
  3. Replies: 1
    Last Post: July 19th 2009, 12:43 PM
  4. Replies: 5
    Last Post: May 10th 2009, 07:25 PM
  5. Replies: 1
    Last Post: April 22nd 2009, 08:43 PM

Search Tags


/mathhelpforum @mathhelpforum