Just plug Yp into the DE and equate like powers of x (the exponentials will cancel, I think). Where does that place you?
ok so here is the problem
y'' +3y = -48(x^2)(e^3x)
ok so i get the first few couple of steps,
m^2 +3 = 0, m = +/- sqrt(3)i
so Yc = C1cos sqrt(3)x + C2sin sqrt(3)x
Yp = (Ax^2 +Bx + C)e^3x
so how do i find Yp? well let me ask first, is my setup right so far?
i need a lil help on this one....