例： Z(s)=s(s2+4) s2+1 u N Z(s)= 3s s2+1 +S K,=limn[x网s+] 2-0 pn im 3H s2-1 i X(S)→ N 3s 1 s2+1 1 1 S十 3 3s C.K X2(S) L= pnu1 1 i N ] 3 1 1 ( 4) [ [ ( ) ] 2 2 2 1 2 2 1 lim lim 2 2 2          s s s s s s s K X s s p n s n p n   s s s s 3 1 3 1 1 1 3 2    n n K C 1  1 i N1 X2 (s) X1 (s) 2 pn n n K L   1 ( 4) ( ) 2 2    s s s Z s s s s Z s    1 3 ( ) 2 例： 1/3F 3H