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Math Help - Help please

  1. #1
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    Help please

    If I have the second order differential equation

    y'' + y = 0

    The auxilliary equation is

    m^2 + m = 0

    The two solutions are therefore

    m = 0, -1

    so

    y = A*exp(0*x) + B*exp(-1*x)

    Is this correct?

    My notes say the solution is

    y = C1*cos(x) + C2*sin(x)

    can anyone explain please
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  2. #2
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    mr fantastic's Avatar
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    Quote Originally Posted by revolution2000 View Post
    If I have the second order differential equation

    y'' + y = 0

    The auxilliary equation is

    m^2 + m = 0 Mr F says: This is wrong. This is the auxillary equation for y'' + y' = 0.

    The two solutions are therefore

    m = 0, -1

    so

    y = A*exp(0*x) + B*exp(-1*x)

    Is this correct?

    My notes say the solution is

    y = C1*cos(x) + C2*sin(x)

    can anyone explain please
    The auxillary equation for y'' + y = 0 is m^2 + 1 = 0.
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  3. #3
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    Thank you Mr. Fantastic you truly are
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