Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

D'Alembert Ratio Test: Convergence test

  1. Apr 18, 2010 #1
    Hi this is just a general question about using the ratio test for convergence.

    If I have to carry out the test to find out if something converges (and I don't need to find out if its absolutely converges, but just convergence), then can my answer to the test be negative?

    Or does the formula for the ratio test when finding the limit, use the modulus?
  2. jcsd
  3. Apr 18, 2010 #2


    User Avatar
    Science Advisor

    Strictly speaking, the ratio test only applies to sequences of positive numbers so, yes, it applies to the modulus (absolute value).
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook