1. Not finding help here? Sign up for a free 30min 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!

Integrate by substitution

  1. May 12, 2009 #1
    1. The problem statement, all variables and given/known data
    The problem states: Use substitution to solve:

    y'=1/(x+y)^2-1


    2. Relevant equations



    3. The attempt at a solution

    I used the substitution of v=x+y

    resulting in the answer y=[3(x-C)]^(1/3) - x

    but I'm not too sure that's right

    Can some help with the answer and the steps for getting it. It's just for a practice test so I'm not graded on it.
     
  2. jcsd
  3. May 12, 2009 #2

    rock.freak667

    User Avatar
    Homework Helper

    Show all of the steps you took to get the correct answer. If you made an error in any step, we could point it out then.
     
  4. May 12, 2009 #3

    gabbagabbahey

    User Avatar
    Homework Helper
    Gold Member

    It looks like you got to [itex](x+y)^3=3x+C[/itex] correctly (you probably had -3C instead of +C but it makes no difference since both are just undetermined constants) ? ...If so, this is how you should leave your answer (unless you are given a point on the curve y(x)). The reason being is that there are actually three roots to this cubic equation, and [itex]y+x=\sqrt[3]{3x+C}[/itex] is only one of them.
     
  5. May 12, 2009 #4
    Great! So overall I got the problem right. Thanks.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: Integrate by substitution
  1. Integral substitution? (Replies: 3)

  2. Integral substituting (Replies: 4)

Loading...