... so.d¯ˆo`du.´o.i d¯ˆay:(7263 148 5) (615283 74) (5 841 7263)(35 841 726) (46 152837) (57263 148 )(1683 742 5) (572631 84) (48 157263)(5 146 8273) (42 751863) (35281 746 )Mˆo˜i so.d¯ˆo`trˆen tu.o.ng ... tu.˙’nho˙’nhˆa´t-l`a β(G). Trong v´ı du.n`ay, β(G) = 4 v`a c´ac tra.m g´ac cˆa`n d¯ˇa.t ta.i c´ac vi.tr´ı{3, 5, 12, 14} hoˇa.c ta.i {2, 9, 15, 8}.V´ı du.2 .4. 6 B`ai to´an vˆe`5 ... hˆa.u, chˇa˙’ng ha.n v´o.i hai c´ach sˇa´p xˆe´p:(3, 3), (4, 6), (5, 4) , (6, 2), (7, 5)v`a(5, 1), (8, 3), (4, 4) , (3, 6), (7, 8),trong d¯´o (i, j) l`a vi.tr´ı cu˙’a con hˆa.u...