1, Independence number $\alpha(G)$ is maximum number of pairwise nonadjacent vertices of $G$.
2, The chromatic number X(G) of G is the minimum number of colors in a coloring of the vertices of G with the property that no two adjacent vertices have the same color.
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[RIGHT][I][B]Nguồn: MathScope.ORG[/B][/I][/RIGHT]