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: Just couldnt figure this out =

  1. Oct 31, 2008 #1
    why the equivalence??????

    there must be some formula for this...just i donno.
    i really need some hints!!! thank you guys!

    Attached Files:

  2. jcsd
  3. Oct 31, 2008 #2


    User Avatar
    Homework Helper
    Gold Member

    The derivative operator [itex]\frac{\partial^j}{\partial x^j}[/itex] is acting only on x...the j=0 derivative is just the zeroith order derivative of x, which is x. The j=1 derivative is [itex]\frac{\partial}{\partial x}x=1[/itex]. Since this is a constant, all higher order derivatives are zero and so all the j>1 terms in each of the sums is zero. You are left with only the j=0 and j=1 terms which you can write out explicitly to obtain the expression on the right.
  4. Oct 31, 2008 #3

    Now i understand why it goes like that!!!
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook