1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: Series/Convergence help

  1. Dec 7, 2005 #1
    help determining where the series here is abs. convergent.

    its Sin(2n)/n^2, i thought about the ratio test but it gets nasty, is there a easier way?
    nm, i think it is convergence if I use the comparison test? Sound right?

    what about (-3)^n/n!, i used the ratio test, and got 0, which means it abs. convergent since 0<1, but i dont think i did it right .
    I did:
    Lim n-> infinity : (-3^(n+1)/(n+1)!)(n!/-3^n)= -3 lim n!/n+1!....
    does that look right?
    Last edited: Dec 7, 2005
  2. jcsd
  3. Dec 7, 2005 #2


    User Avatar
    Homework Helper

    On the 1st one: what about the comparison test to its absolute value series?

    On the 2nd one: Consider the Ratio Test or d'Alambert's ratio.
    Last edited: Dec 7, 2005
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook