(2)消去单环 E 1-Srs a S21b2 1-SF a (3)分裂a2 E 1-Srs a b a1- S11Gg 1 a1 2 a b2 g g S S - G G 11 12 1 S22 S21 GL （ E 2）消去单环 （3）分裂a2 1- S11Gg 1 a1 2 a b2 g g S S - G G 11 12 1 S22 S21 GL E GL 2 a