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: Separation of variables

  1. Sep 29, 2008 #1
    1. The problem statement, all variables and given/known data

    so here's my equation:


    so what i did first was factor out the right side


    then i did a bunch of manipulation to get the ys on one side and the xs on another (i won't write this out right now but if anyone wants me to i can)

    and got

    (y-2)/(y+3) dy = (x-1)/(x+4) dx

    of course i integrate, i get

    y-5*ln(y+3) = x-5ln(x+4)

    i want to get rid of the lns, right? so i multiplied them by e (like e^(ln(y+3)

    then i got -4y-15=-4x-20

    i'm not sure what to do after this because i looked at the answer at the back of my book and it said something completely different to what i've done so far, any help?

    2. Relevant equations

    3. The attempt at a solution
  2. jcsd
  3. Sep 29, 2008 #2


    User Avatar
    Homework Helper
    Gold Member

    Shouldn't your exponent for [itex]e[/itex] be the entire expression on each side of the equation?


    [tex] e^{y-5ln(y+3)}=e^{x-5ln(x+4)}[/tex]
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook