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Math Help - Diff

  1. #1
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    Diff

    need help solving this diff plz



    3y - y = 5x
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  2. #2
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    I may be wrong, but i don't think you can solve that because there is only one equation and two unknowns.
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  3. #3
    Moo
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    Quote Originally Posted by nugiboy View Post
    I may be wrong, but i don't think you can solve that because there is only one equation and two unknowns.
    It's a differential equation

    y is a function of x
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  4. #4
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    Quote Originally Posted by Moo View Post
    It's a differential equation

    y is a function of x
    How do you do it then lol?
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  5. #5
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    Hello again, yes I know its a diff equation but I would need some guidence and help solving it =).


    thank you
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  6. #6
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    Quote Originally Posted by mladen View Post
    need help solving this diff plz



    3y - y = 5x
    You can use an integrating factor:

    First
    y' - \frac{1}{3}y = \frac{5}{3}x

    Then
    M(x) = e^{\int(-dx/3)} = e^{-x/3}

    So
    e^{-x/3}y' - \frac{1}{3}e^{-x/3}y = \frac{5}{3}xe^{-x/3}

    Notice that the left hand side of the equation is a "perfect derivative"
    \frac{d}{dx} \left ( e^{-x/3}y \right ) = \frac{5}{3}xe^{-x/3}

    e^{-x/3}y = \int \frac{5}{3}xe^{-x/3}~dx

    I'll let you finish out from there.

    -Dan
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