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When to use partial fraction?

  1. Mar 14, 2009 #1
    1. The problem statement, all variables and given/known data

    do we look at the nominator or the denominator? are we trying to separate them? factoring them?

    thanks
     
  2. jcsd
  3. Mar 14, 2009 #2

    tiny-tim

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    Hi myusernameis! :wink:
    The denominator. And you factor it. :smile:
     
  4. Mar 14, 2009 #3
    thanks for the answers!

    so let's say i have this long equation in denom.

    [tex]\frac{1}{(s^2+1)(s^2+4s-12)}[/tex]

    i can factor one of them to look like:

    [tex]\frac{1}{(s^2+1)(s+6)(s-4)}[/tex]

    but then how do I know if I should use A +B or As+B, Cs+D, etc..?
     
  5. Mar 14, 2009 #4

    tiny-tim

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    erm :redface: … nooo!
    sorry, not following you …

    for a linear denominator, it's just a number on the top,

    for a quadratic denominator, it's a linear top :smile:
     
  6. Mar 14, 2009 #5

    haha made a mistake... so with that, do i use As+ B?

    what if it's (s^2+2)(s^2+3)(s^2+5), ie, several s squares?
     
  7. Mar 14, 2009 #6

    if was supposed to be a (s+6)(s-2)....
     
  8. Mar 14, 2009 #7

    tiny-tim

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    each one has a linear top :smile:
    each one has a number on the top
     
  9. Mar 14, 2009 #8
    ok,

    taking this example again: (s^2+2)(s^2+3)(s^2+5)

    would it be: 1 = (As+B)/(s^2+2)(s^2+3)(s^2+5) + (Cs+D)/(s^2+2)(s^2+3)(s^2+5) + (Es+F)/(s^2+2)(s^2+3)(s^2+5) ?
     
  10. Mar 14, 2009 #9

    tiny-tim

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    uhh? :confused:

    it's 1/(s2+2)(s2+3)(s2+5)

    = (As+B)/(s2+2) + (Cs+D)/(s2+3) + (Es+F)/(s2+5)
     
  11. Mar 14, 2009 #10
    haha brain fart on my part(i hope)


    thanks
     
  12. Mar 14, 2009 #11

    tiny-tim

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    wow! where's your brain? :biggrin:
     
  13. Mar 14, 2009 #12
    are you a math teacher?
    if you don't mind me asking!
     
  14. Mar 14, 2009 #13

    tiny-tim

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    i'm just a little goldfish …

    trying to make sense of the bowliverse! :smile:
     
  15. Mar 14, 2009 #14
    haha! well, thanks for the help!
     
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