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Math Help - Dif EQ

  1. #1
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    Dif EQ

    Verify that the function is a sol'n of the given differential equation:

    t*dy/dt - y = t^2, y = 3t + t^2

    So I worked with y = 3t + t^2

    y' = 3 + 2t
    y'' = 2

    Then, t*dy/dt - (3t + t^2) = t^2 .. so if it did work, that means t*dy/dt = 3t, but I don't seen how.
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  2. #2
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    Quote Originally Posted by Ideasman View Post
    Verify that the function is a sol'n of the given differential equation:

    t*dy/dt - y = t^2, y = 3t + t^2

    So I worked with y = 3t + t^2

    y' = 3 + 2t
    y'' = 2

    Then, t*dy/dt - (3t + t^2) = t^2 .. so if it did work, that means t*dy/dt = 3t, but I don't seen how.
    Why did you take the second derivative?

    Subbing the solution in I get:
    t \cdot (3 + 2t) - (3t + t^2) = t^2

    3t + 2t^2 - 3t - t^2 = t^2

    t^2 = t^2 (Check!)

    -Dan
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