Results 1 to 4 of 4

Math Help - y`=y+2 Seems Simple, but i can't match the answer up to it.

  1. #1
    Newbie
    Joined
    Apr 2011
    Posts
    7

    y`=y+2 Seems Simple, but i can't match the answer up to it.

    The equation is:
    dy/dx=y+2

    The answer is y=Cex-2

    Can anyone explain this?
    Follow Math Help Forum on Facebook and Google+

  2. #2
    Member
    Joined
    Dec 2011
    Posts
    92
    Thanks
    7

    Re: y`=y+2 Seems Simple, but i can't match the answer up to it.

    The answer looks correct. You can easily check if it's correct yourself by finding the derivative and plugging it back into the equation.
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Member
    Joined
    May 2008
    Posts
    106

    Re: y`=y+2 Seems Simple, but i can't match the answer up to it.

    If you also want to see why write
    the equation is seperable and can be written as
    \int \frac{dy}{y+2} = \int dx

    so
    \ln (y+2) = x + c

    then taxing the exp of both sides and writing the arbitrary constant as C = ln c gives the solution as you have it
    Follow Math Help Forum on Facebook and Google+

  4. #4
    Junior Member
    Joined
    Mar 2009
    Posts
    31

    Re: y`=y+2 Seems Simple, but i can't match the answer up to it.

    Or you can check the answer by taking the derivative of it:

    \frac{d}{dx} y(x) = Ce^x

    So you put this back into the differential equation:

    Ce^x = [Ce^x - 2] + 2

    It turns out to be true.
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. simple questions need answer # 3
    Posted in the Advanced Statistics Forum
    Replies: 1
    Last Post: September 8th 2009, 05:26 PM
  2. simple question need answer #1
    Posted in the Advanced Statistics Forum
    Replies: 0
    Last Post: September 7th 2009, 06:57 PM
  3. simple questions need answer # 4
    Posted in the Advanced Statistics Forum
    Replies: 0
    Last Post: September 7th 2009, 06:57 PM
  4. Answer in Algebra book doesn't match mine!
    Posted in the Algebra Forum
    Replies: 2
    Last Post: June 26th 2008, 09:10 AM
  5. My answer doesn't match the book
    Posted in the Algebra Forum
    Replies: 2
    Last Post: June 20th 2008, 07:30 AM

Search Tags


/mathhelpforum @mathhelpforum