y”-x"+x'-y=e-2 2 "-2y+x=-t 对两个方程取拉氏变换,设[y(O刀Y(s [x()]=X(s),并考虑到初始条件,得 s Y(S)SX(S)+sX(s)-Y(S) 2s2Y(s)-S2X(S)-2.(S)+X(S)= 整理得(s+)y(s)-sX() s+2 S(S-1 2sY()-(S+1)X(s) SS9 对两个方程取拉氏变换, 设L [y(t)]=Y(s), L [x(t)]=X(s), 并考虑到初始条件, 得    - - + = - - + - = - y x y x t y x x y t 2 2 e 2      - - + = - - - - + - = 2 2 2 2 2 1 2 ( ) ( ) 2 ( ) ( ) 2 1 1 ( ) ( ) ( ) ( ) s s Y s s X s sY s X s s s s Y s s X s sX s Y s 整理得        - - + = - - - + + - = ( 1) 1 2 ( ) ( 1) ( ) ( 1) 2 ( 1) ( ) ( ) 2 2 s s sY s s X s s s s s Y s sX s