Let $N = \{1, 2, 3, 4, 5\}$
Let $G$ be an un-directed graph defined as follows:
- Let $VERTS(G)$ denote the vertex set of $G$.
- $N$ subset of $VERTS(G)$
- For all $k$ ∈ $N$, $N/\{k\}$ ∈ $VERTS(G)$
- Specifically,
- {2, 3, 4, 5} ∈ Verts(G)
- {1, 3, 4, 5} ∈ Verts(G)
- {1, 2, 4, 5} ∈ Verts(G)
- {1, 2, 3, 5} ∈ Verts(G)
- {1, 2, 3, 4} ∈ Verts(G)
- Specifically,
The vertices noted above are the only elements of Verts(G) G has a total of 10 verticies.
For all k ∈ N, $\{k, N/\{k\}\}$ is an edge of $G$.
For example, $\{1, \{2, 3, 4, 5\}\}$ is an edge of $G$
Also, For all $k$ in $N$,
for all $p$ ∈ N/{k}
{N/{k}, p} is an edge of $G$.
For example,
{{2, 3, 4, 5}, 2} is an edge of G.
G has a total of 25 edges.
Question: is $G$ a planar graph? Can it be drawn on the Cartesian plane without any two edges crossing each other?
I drew the graph in paint, and started adding in edges, but I didn't finish adding edges. It looks non-planar, I think:

Without having to read beyond the title, the answer must be no. A simple planar graph on $n$ vertices can have at most $3n-6$ edges.