申論題

6. The girth of a graph G is the length of the shortest cycle in G. Let G be a simple graph with y vertices, e edges, and girth g. It is known that if G is planar, then e . Let K₅ be a complete graph with 5 vertices, K₅and K₃,₃ be a complete bipartite graph with 3 vertices in each partition. Draw Ks and K₃,₃, and show that they are not planar.