C(s) G+G2 2-17(a)R(s)1+G2G3 (b)=a+2 1111 C(s) (G+G3)G R(S)1+G2H,+G G2H,(d) R(S)I+GH,+G2H2+G3H3+G,HGWs (e) Cs)_Sx1+02H1-G GH, +G,GH2 (f) C(s)_(G,+G3)G2 R(S) R(S) 1+G GrH C(s) G,G2 2-18(a)ws)1+G1G2+G1G2H1 C(s)G3G2-(1+G1G2H1) NS)1+G,G2+G GrHI b) C(s)-(+G1)G2 G4+G3G C(s) G R(s)1+G2G4+G3G4 N(s)1+G2G4+G3G4 2-19与2-17同2-20与2-18同 2-21(a)R=1+,且1+G2H2+6M1B2+6,HG,H2 E(S (1+G3H2)-GG;H2H1 R(S)1+G,H,+GH,+GG,G,H,H2+GHG,H (b)C(s) G1-G2-2G1G2 C(s) 1-G1G2 R(s)1-G1-G2-3G1G2 R(s)1-G1-G2-3G1G2（2-17题~2-21题） 2-17(a) 2 3 1 2 1 G G G G R(s) C(s) + + = (b) 1 1 1 2 1 2 1 2 1 G H H H G G (1 H H ) R(s) C(s) − + + = (c) 2 1 1 2 2 1 3 2 1 G H G G H (G G )G R(s) C(s) + + + = (d) 1 1 2 2 3 3 1 1 3 3 1 2 3 1 G H G H G H G H G H G G G R(s) C(s) + + + + = (e) 2 1 1 2 1 2 3 2 1 2 3 4 1 G H G G H G G H G G G G R(s) C(s) + − + = + (f) 1 2 1 1 3 2 1 G G H (G G )G R(s) C(s) + + = 2-18(a) 1 2 1 2 1 1 2 1 G G G G H G G R(s) C(s) + + = 1 2 1 2 1 3 2 1 2 1 1 G G G G H G G (1 G G H ) N(s) C(s) + + − + = (b) 2 4 3 4 1 2 4 3 4 1 G G G G (1 G )G G G G R(s) C(s) + + + + = 2 4 3 4 4 1 G G G G G N(s) C(s) + + = 2-19与2-17同 2-20与2-18同 2-21(a) 1 1 3 2 1 2 3 1 2 1 1 3 2 1 2 3 4 3 1 1 1 G H G H G G G H H G H G H G G G G G (1 G H ) R(s) C(s) + + + + + + = 1 1 3 2 1 2 3 1 2 1 1 3 2 3 2 4 3 2 1 1 G H G H G G G H H G H G H ( 1 G H ) G G H H R( s ) E( s ) + + + + + − = (b) 1 2 1 2 1 2 1 2 1 G G 3G G G G 2G G R(s) C(s) − − − − − − = 1 2 1 2 1 2 1 G G 3G G 1 G G R(s) C(s) − − − − =