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Math Help - Another undetermined coeffceint

  1. #1
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    Another undetermined coeffceint

    y'' - 2y' +5y = e^X cos(2x)

    im just a bit lost on this one...i know the sub will be Ae^x cos 4x + B e^x sin 4x ....
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  2. #2
    is up to his old tricks again! Jhevon's Avatar
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    Quote Originally Posted by neven87 View Post
    y'' - 2y' +5y = e^X cos(2x)

    im just a bit lost on this one...i know the sub will be Ae^x cos 4x + B e^x sin 4x ....
    no, we will guess a particular solution of the form:

    y_p = Axe^x \cos 2x + Bx e^x \sin 2x

    since the homogeneous solution is of the form A e^x \cos 2x + B e^x \sin 2x we can't choose that as the particular solution, you'll end up with zero, so we add a factor of x
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