1X1=1 X,=1 3 1X1+612X2+813X3+△p=0 1X1+O12X2+△1p=0 621X1+62X2+623X3+△2p=0 621X1+022x2 X,+△ 2P 631X1+o32x2+63x3+△yP=0 3343 +△3 P 0 P 0.5P0.5P 0.5P0.5P M PX 2 X 1 2 = X1 X1 = 1 M1 M2 M3  + + +  = + + +  = + + +  = 000 3 1 1 3 2 2 3 3 3 3 2 1 1 2 2 2 2 3 3 2 1 1 1 1 2 2 1 3 3 1 PPP X X X X X X X X X           +  = + +  = + +  = 000 33 3 3 21 1 22 2 2 11 1 12 2 1 PPP X X X X X      0 . 5 P 0 . 5 P 0 . 5 P 0 . 5 P M P MP X 1 3 =X3 P 5