o1+o2=Q4/S ① (Q=const.) o3十o4=QB/S (QB=const.) 61-02-03-04=0 ③ (EA=0) 01+02十03-04=0 ④ (EB=0) ③④→ 01-04=0 (外侧 等量同号！) 0203=0 ⑥ (内侧 等量异号！)1+2=QA/S ① (QA=const.) ③④→ 1 -4=0 ⑤ 2+3=0 ⑥ (外侧——等量同号!) (内侧——等量异号!) 3+4=QB /S ② (QB=const.) 1 -2 -3 -4=0 ③ (EA=0) 1+2+3 -4=0 ④ (EB=0)