P5 - 2nd Diff Equ... Watch
just going through this qu:
d2y/dx^2 - 3dy/dx - 4y = 50sin2x
I get y = Ae^4x + Be^-x + 3cos2x - 4sin2x
I am told x=0 y=0 thus A + B = -3
and as x tends to infinite y is finate, eventually and i need to find y in terms of x, this part is where im stuck, i am aware that A and B will have to be solved simultaniously, but what happens when x tends to infinite and y is finate?
If x -> infinite, e^-x tends to 0, e^4x tends to infinite.
So Ae^4x + Be^-x tends to infinite -> y tends to infinite.
Therefore A = 0, so B = -3