General solution for ordinary differential equation $y'' + 9y = 18x + 36 \sin 3x$

General solution for ordinary differential equation $y'' + 9y = 18x + 36
\sin 3x$

Find a (real) general solution for
$$y'' + 9y = 18x + 36 \sin 3x$$
I need some help in finding the solution, have been struggling for long.
My answer does not match with the final answer which is:
$$y_h = A\cos 3x + B\sin 3x $$ $$y_p = 2x - 6x\cos 3x$$