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!

Progressive terms assumption!

  1. Apr 23, 2012 #1
    "If we have to take three terms in an AP, it is convenient ti take them as a-d,a,a+d. In general, we take a-rd,a-(r-1)d,....,a-d,a,a+d, in case we have to take (2r+1) terms in an AP."

    What do they mean by the portion in bold?
    What is 'r' here ?
  2. jcsd
  3. Apr 23, 2012 #2


    User Avatar
    Science Advisor

    r is an integer related to the total number of terms in the sequence (2r+1). I am not aware of the context.

    The author (for some reason) is counting an arithmetic progression with an odd number of terms by starting in the middle and counting r terms in each direction. I have no idea what the point is. Usually a discussion of AP will start with the first term, while the number of terms may be odd or even.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook