故,一般强迫振动的解: u=u+u 为: =[o(x+a)+0(x-ar y(ada x+a(t-t) f(a, t)dadi故，一般强迫振动的解： I II u = u + u 为： [ ] ò ò ò + - - - + - + + = + + - t x a t x a t x at x at f d d a d u x at x at 0 ( ) ( ) ( , ) 2 1 ( ) 2 1 ( ) ( ) 2 1 t t a t a t y a a j j