E=(r+R1)l1
E=(r+R1)l2
E=r×l1+R1×l1 =>r×l1=E-R1×l1=>r=E/l1-R1
E=(E/l1-R1+R2)l2
E=E×l2/l1-R1×l2+R2×12
E-E×l2/l1=R1×12+R2×l2
E(1-l2/l1)=R1×l2+R2×l2
E(1-0,2/0,14)=7×0,2+4×0,2
E(0,14-0,2)/0,14=3×0,2
E(0,06/0,14)=3×0,2
E=0,6×0,14/-0,06
E=1,4V
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