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: Quick question I'm having trouble with (partial fraction integration)

  1. Jan 13, 2010 #1
    Ok, so why do some answers contain an A/something + (Bx + C)/something and others contain just an A/something + B/something.

    I hope someone knows what I'm talking about!
     
  2. jcsd
  3. Jan 14, 2010 #2

    Mark44

    Staff: Mentor

    Yes, I know what you're talking about. It depends whether the factors in the denominator are linear factors or irreducible quadratic factors.

    For example, with 3/[(x - 1)(x2 + 1)], the x - 1 factor in the denominator is a linear factor (x is to power 1) and x2 + 1 is an irreducible quadratic. The decomposition would look like this:
    3/[(x - 1)(x2 + 1)] = A/(x - 1) + (Bx + C)/(x2 + 1)

    To reduce 3/[(x - 1)(x - 2)], both factors in the denominator are linear factors, so the decomposition would look like this:
    3/[(x - 1)(x - 2)] = A/(x - 1) + B/(x - 2)

    If you have repeated linear factors, such as 5/[(x - 1)2, things are a little different and the decomposition would be this:
    5/[(x - 1)2 = A/(x - 1) + B/(x - 1)2

    Hope that helps.
     
  4. Jan 14, 2010 #3
    Thank's Mark, that makes complete sense. I was confused when the seemingly random x would tag onto an A or B term and i had no idea why. Thanks again for clarifying.
     
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook