Hi guys, I've got this differential equation:

$\displaystyle \ddot{y}+y=4sin{\alpha{x}}$

And I've worked out the general solution when it is set equal to zero to be:

$\displaystyle Acos{x}+Bsin{x}$

I need help finding the equation to set y(x) to so that i can solve the rest of it. Any clues?

Thanks in advance