1+ A I+B,xr, r B2R4 R1=R1∥[1+(1+B1R2∥R3∥re2) R。=R4 ≈BR2∥h+(+B2DD B2R3 R1 +(1+B2)r R1=R1 R。=R3 A=[-gm(R4∥R6∥R7∥k2) BaRs R1=R3+R1∥R R。=R8 3.3(1)(d)(e)(2)(c)(e)(3)(e) 3.4图(a) Pu 2=B An=An1·An2 R1=R1∥R2∥ret≈0 R。=R3=3k B1·(R1∥ra2) B,R An=Aa1·An2≈2100 R1=(R5+R2∥R3)∥rm1≈1.2kg R。=R4=1k 3.5图(c)12 o 4 i 1 be1 1 2 3 be2 be2 2 4 be1 1 2 3 be2 1 2 3 be2 [ (1 )( )] ( ) (1 )( ) (1 ) R R R R r R R r r R r R R r R R r Au = = + + − + + + = − ∥ ∥ ∥ ∥ ∥ ∥ ∥ 图(c) o 3 i 1 be1 be2 2 2 3 1 be1 1 2 be2 2 ] (1 ) [ [ (1 ) R R R R r r r R R r R r r A D D u = = + + + − + + + = ∥ 图(d) o 8 i 3 1 2 be2 2 8 m 4 6 7 be2 [ ( )] ( ) R R R R R R r R A g R R R r u = = + = − − ∥ ∥ ∥ ∥ 3.3 (1)(d)(e) (2)(c)(e) (3)(e) 3.4 图(a) = = = = − = = + − = 3k 0.93k 125 125 1 o 3 i 1 2 be1 1 2 be2 2 3 2 be1 2 be2 1 1 R R R R R r A A A r R A r r A u u u u u ∥ ∥ 图(b) = = = + = = − − − = 1k ( ) 1.2k 2100 42 50 ( ) o 4 i 5 2 3 be1 1 2 be2 2 4 2 be1 1 1 be2 1 R R R R R R r A A A r R A r R r A u u u u u ∥ ∥ ∥ 3.5 图(c)