I know that in order for the $6$-vertex graph to be non planar, it needs to contain more than $12$ edges. I tried drawing some picture to find the graph, but run out of ideas. It's easy to find the planar one, but not the non planar one.
Any ideas?
I know that in order for the $6$-vertex graph to be non planar, it needs to contain more than $12$ edges. I tried drawing some picture to find the graph, but run out of ideas. It's easy to find the planar one, but not the non planar one.
Any ideas?
I'm not sure what you mean by your first sentence - the complete bipartite graph $K_{3,3}$ is non-planar and it only has $9$ edges. And in fact (hint) if you make a small modification to this graph I think you will have an answer to your question.