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: General Formula using Miscellaneous Substitution

  1. Nov 1, 2006 #1
    I'm really stomped with this problem... i can't seem to get the answer...

    anyway... here's the problem..

    (2(x^3) - (y^3))y'=3(x^2)y

    and i need to get the general solution....

    SO, here's what i did...

    I Let
    u=x^3 and
    du=3x^2dx

    so what happens is

    2udy-(y^3)dy= ydu

    and that's where i got stuck...

    i tried using
    d(y/u)=(udy-ydu)/u^2

    but i can't seem to get rid of the 2 in 2udy and it would be much of a problem if i did that...

    could anyone help me??
     
  2. jcsd
  3. Nov 1, 2006 #2

    arildno

    User Avatar
    Science Advisor
    Homework Helper
    Gold Member
    Dearly Missed

    Rewrite this diff.eq as:
    [tex]y'=\frac{3\frac{y}{x}}{2-(\frac{y}{x})^{3}}\equiv{F}(\frac{y}{x}[/tex]

    I'm sure you have solved such problems previously.
     
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook