s+2 S(S 1) (s+1) (S-1) S S(s-2)s+1)-s+1 S(S-1) s+ S(S 1) S-2-s+1 2S-1 s(s-1)2 S(S 由上讲例2可得 Y(S) Ds(s-1)2y()=1+t11 t t Y Y D s s y t t D Y s s s s s s s s s s s s s s s s s s s s s s s s s s s s s D ( ) 1 e e 2 ( 1) 1 ( ) ( 1) 2 1 ( 1) 2 1 ( 1) ( 2)( 1) 1 1 1 2 ( 1) 1 ( 1) ( 1) 1 ( 1) 2 2 2 2 2 2 2 2 2 2 - = + - = = - - - = - - - - + = - - + - + = + - - - = - + - - - - - + = 由上讲例 可得