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: Logarithmic series

  1. May 19, 2007 #1
    Find the coefficient of x to the power n in the expansion of

    log e ( a + bx + cx2 ) where a,b,c,n belong to R.

    (Note: cx2 means it is c x (X square ) and e is base for which the above logarithm is defined.)
  2. jcsd
  3. May 19, 2007 #2
    Using the Taylor expansion and the Binomial theorem gives an ugly expression...
  4. May 19, 2007 #3
    factor and take derivative. then expand using geometric series. integrate afterward.
  5. May 20, 2007 #4
    Werg22 and tim_lou thanks.But guys!!!!! I have already tried those techniques but I have not got an accurate to the point answer.As Werg22 says I am getting an ugly expansion of no significance.I am still far away from getting a simplified answer.Tim_lou, if you are getting a simplified answer then what is it?????????
  6. May 21, 2007 #5
    Is there an expansion of 1/x? If so, you could easily do it for a + bx + cx2 that has real solutions.
  7. May 21, 2007 #6
    O.K.I will try that.Werg22 , Please give me the final answer so that I can verify it.
  8. May 21, 2007 #7
    I actually do not know of the expansion of 1/x...
  9. May 22, 2007 #8
    Use binomial expansion of (0 + x) to the power -1.
  10. May 22, 2007 #9


    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    1/x is the (only Laurent) expansion for 1/x about the point x = 0.

    It's against our policy to hand out answers.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook