即Y(s)有三个单极点为-1,1,3 s+2 s+2 Y(S) (s+1)s2+2s-3)s3+2s2-3s+s2+2s-3 s+2 A(S) s3+3s2-s-3B(s) B(s)=3s2+6s-1,因此 1+2 1+2 3+2 v(t) e+ e+ 3-6-1 3+6-127-18-1 3,1 e+=e7 即Y(s)有三个单极点为-1,1,-3 t t t t t t y t 3 3 e 8 1 e 8 3 e 4 1 e 27 18 1 3 2 e 3 6 1 1 2 e 3 6 1 1 2 ( ) - - - - = - + - - - - + + + - + + - - - + = B'(s)=3s 2+6s-1, 因此 ( ) ( ) 3 3 2 2 3 2 3 2 ( 1)( 2 3) 2 ( ) 3 2 2 3 2 2 B s A s s s s s s s s s s s s s s s Y s = + - - + = + - + + - + = + + - + =