关于block的几个理解 Theorem 5.7 A graph of order at least 3 is nonseparable if and only if every two vertices lie on a common cycle. x u Uk-1 Uk=U 问题4：从这个定 理及证明中能否 看出，非分离图 在外表上具有什 么共性？关于block的几个理解 Theorem 5.7 A graph of order at least 3 is nonseparable if and only if every two vertices lie on a common cycle. 问题4：从这个定 理及证明中能否 看出，非分离图 在外表上具有什 么共性？