Results 1 to 3 of 3

Math Help - Initial Value Problem

  1. #1
    Newbie
    Joined
    Jan 2009
    Posts
    20

    Question Initial Value Problem

    dy/dt + 0.8ty = 2t
    y(0) = 9
    This is what I have so far
    dy/dt = 2t - 0.8ty
    dy/(2- 0.8y) = t dt
    y/2 - 0.8ln|y| = (t^2)/2 + C
    Solve C:
     C = (9/2)-0.8ln|9|

    Now I'm having trouble isolating Y to get an answer.
    Have I taken all the right steps so far, and if so how do I go about isolating Y?
    Thank You for any help
    Follow Math Help Forum on Facebook and Google+

  2. #2
    MHF Contributor Calculus26's Avatar
    Joined
    Mar 2009
    From
    Florida
    Posts
    1,271
    there are 2 things on this one


    1. Since this is a linear DE the whole problem can be solved easier using an integrating factor

    is set up perfectly for this

    with the integrating factor e^(.4*t^2)

    However suppose you want to separate variables

    2.first you were ok up to



    To integrate the left use u = 2 - 0.8y

    you tried to write as dy/2 -dy/(.8y) which is not true
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Newbie
    Joined
    Jan 2009
    Posts
    20
    Whoa I didn't not even see that it was a integrating factor problem haha thank you very much.
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. DE Initial Value Problem
    Posted in the Differential Equations Forum
    Replies: 4
    Last Post: March 3rd 2011, 10:21 PM
  2. initial value problem
    Posted in the Differential Equations Forum
    Replies: 4
    Last Post: January 1st 2011, 02:49 AM
  3. Initial value problem
    Posted in the Differential Equations Forum
    Replies: 4
    Last Post: November 11th 2010, 12:33 PM
  4. initial value DE problem
    Posted in the Differential Equations Forum
    Replies: 6
    Last Post: December 15th 2009, 03:10 PM
  5. Initial Value Problem?
    Posted in the Calculus Forum
    Replies: 4
    Last Post: May 21st 2009, 04:30 PM

Search Tags


/mathhelpforum @mathhelpforum