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jrsweet
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Homework Statement
Find a particular solution to the differential equation
2 y'' - 1 y' - 1 y = -1 t^2 + 2 t + 3 e^{4 t} .
Homework Equations
The Attempt at a Solution
I have attempted this problem many times. I think I am having trouble assuming what the general form is.
assume yp=(At+B)^2+Ce^(4t)=(A^2)(t^2)+2ABt+(B^2)+Ce^(4t)
yp'=2(A^2)t + 2AB + 4Ce^(4t)
yp''=2(A^2)+16Ce^(4t)
So, 2yp''-yp'-yp= 4(A^2)+32Ce^(4t)-2(A^2)t-2AB-4Ce^(4t)-(A^2)(t^2)-2ABt-(B^2)-Ce^(4t)
So, 27Ce^(4t)=3e^(4t) => C=(1/9)
-(A^2)(t^2)=-t^2 => A=1
t(-2(A^2)+2AB) = 2 => B=2
4(A^2)-2AB-(B^2)=0 ... but it doesn't work.
I have tried this problem multiple times in multiple different ways this being my last attempt. It's for an online homework and I can't seem to get the right answer, although I feel like I do it right every time...