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: I can't seem to do this with partial fractions

  1. Jan 31, 2012 #1
    1. The problem statement, all variables and given/known data

    [itex]\frac{x}{(x+4)^{2}}[/itex]

    2. Relevant equations



    3. The attempt at a solution

    I make the integrand equal to the following:

    [itex]\frac{A}{(x+4)}[/itex]+[itex]\frac{Bx+C}{(x+4)^{2}}[/itex]

    Then after finding a common denominator I get

    x = A(x+4)[itex]^{2}[/itex]+(Bx+C)(x+4)

    But that cannot be possible because when you set x=-4, you get -4=0. Any help please?

    Also if you have ANY tips whatsoever about partial fractions please tell me them!
     
  2. jcsd
  3. Jan 31, 2012 #2

    SammyS

    User Avatar
    Staff Emeritus
    Science Advisor
    Homework Helper
    Gold Member

    Algebra check:

    [itex]\displaystyle\frac{x}{(x+4)^{2}}=\frac{A}{(x+4)}+ \frac{Bx+C}{(x+4)^{2}}[/itex]

    Multiplying by (x+4)2 gives:

    [itex]\displaystyle x=A(x+4)+Bx+C[/itex]
     
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook