By Corollary 1.5.4, the complete graph 
is not planar, as a planar graph on five vertices can have at most nine edges. The complete bipartite graph 
has girth 4; this graph is not planar by Theorem 1.5.3, as it has more than eight edges. Show that the graphs which arise by omitting one edge e from either or are planar. Give plane realizations for / e and / e which use straight line segments only.