3.插入网络后 0- [S] 0 r==0 A=E+工b=b1《 a,=Tb,=0 3. 插入网络后 [S] Z L Z g AC g G L G a 1 b 2 b 1 a 2 a 1 = E + G g b 1 = E G = G = 0 g L a 2 = G L b 2 = 0