... 2) (1 2) (1 ) (1 3 2) (1 2 3) (2 3) (1 3 )( 1 3) (1 3) (1 2 3) (1 ) (1 3 2) (1 2) (2 3 )( 2 3) (2 3) (1 3 2) (1 2 3) (1 ) (1 3) (1 2 )( 1 2 3) (1 2 3) (1 3) (2 3) (1 2) (1 3 2) (1 )( 1 3 2) (1 3 2) (2 3) ... S3l`a:123123k.h.= (1 ) ,123213k.h.= (1 2), 123321k.h.= (1 3) ,123132k.h.= (2 3), 123231k.h.= (1 2 3) ,123312k.h.= (1 3 2) .(1 ) (1 2) (1 3) (2 3) (1 2 3) (1 3 2 )( 1 ) (1 ) (1 2) (1 3) (2 3) (1 2 3) (1 3 2 )( 1 ... y) ∈ G, (x, y) ∗ (1 x,−y) =(1 , 0) = (1 x,−y) ∗ (x, y).Vˆa.y G l`a mˆo.t nh´om.b) (1 , 0) = (1 ,k(1−1 1)) ∈ Hknˆen Hk= ∅.∀(x, k(x−1x )) , (y, k(y −1y )) ∈ Hk,(x, k(x−1x )) (y, k(y−1y )) 1=(x, k(x−1x )) (1 y,k(1y−y))...