R1=R1∥[1+(1+B1R2∥R3∥re2) R。=R4 ≈BR2∥h+(+B2DD B2R3 R1 +(1+B2)r Ri=R+rhel R。=R3 4=-gn(R1∥B6∥B∥k2小(B2R3 R1=R3+R1∥R2 R。=R8 3.3(1)(d)(e)(2)(c)(e)(3)(e) 3.4图(a) B +B2 B2R3 125 A=An·An2≈-125 R1=R1∥R2∥r!≈0.93kg R;=R3=3k2 B1·(R1∥re2) B2R An=An1·A12≈2 R1=(R5+R2∥R3)∥rhe1≈1.2k Ri=R4=lkQ2 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 i 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 ( ) i 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）