Let [b]G[/b] be a simple graph, [b] v [/b]and [b]w[/b] — not adjacent vertices.[br]Let [b]G[sub]+[/sub][/b] obtained from [b]G [/b]by connecting v and w, and  graph [b]G[sub]=[/sub] [/b]— by  combining  vertices [b]v[/b] and [b]w [/b]in one.[br][i][size=100]Then[/size][/i]