图的连通性和牢固程度是图结构的重要特性 Theorem 1.10 Let G be a graph of order 3 or more.Then G is connected if and only if G contains two distinct vertices u and y such that G-u and G-y are connected. Theorem 1.8 Let G be a graph of order 3 or more.If G contains two distinct vertices u and y such that G-u and G -v are connected,then G itself is conected. Theorem 1.9 If G is a conected graph of order 3 or more, then G contains two distinct vertices u and v such that G-u and G-v are connected. 这个定理给了你什么直观感觉？图的连通性和牢固程度是图结构的重要特性 这个定理给了你什么直观感觉？