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: Ratio test, why does the (-1)^(n+1) disappear?

  1. Dec 1, 2004 #1
    In the book while doing the ratio test:

    as n --> infinity

    why do they just have (-1)^(n+1) just disappear in the next step, since it oscillates between -1 and 1, I don't understand how u could just make it disappear in computations. Isn't the limit as n -> infinity , equal to D.N.E.?
     
  2. jcsd
  3. Dec 1, 2004 #2
    I believe the ratio test tests the absolute value of |An+1 / An|. so the (-1)^n and (-1)^n+1 will just be one, so u can just take it out.
     
  4. Dec 1, 2004 #3
    crap lol, i didn't even think of that. THanks cyrus, u da man!
     
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook