... 1x2xx3 +x1x23x + x1x2 x3+ x12xx3. 2) f = 1x2x3x +1x2xx3 +1xx2 x3+ x12xx3. 3) f = 1x2x3x4x+ 1xx23x4x+1x2x x34x+1xx2x3 +x12x3x4x +x12x3xx4 + x12xx34x. 4) f = (43xx ... x1x2x3x4 Liên kết x1x2x3x4 2 0010 1 2 0010v 2 ,3 001-v 2 ,3, 6,7 0-1 - 3 0011 3 0011v 2,6 0-1 0v 2,6 ,3, 7 6 0110 2 6 0110v 3, 7 0-1 1v 6,7,14,15 -1 1- 12 1100 12 1100v 6,7 011-v 6,14,7,15 7 ... 7 0111 7 0111v 6,14 -1 10v 12,14, 13, 15 1 1-- 13 1101 3 13 1101v 12, 13 110-v 14 1110 14 1110v 7,15 -1 11v 15 1111 4 15 1111v 13, 15 1 1-1 v 14,15 111-v Tổ...