Humorous Chalk server converse theorem planar graph euler formula holds Any pit Useful
Dual graph - Wikipedia
Euler's formula for connected planar graphs - Mathematics Stack Exchange
Planar Graphs
Planar graph - Wikipedia
SOLVED: Prove that the converse of theorem 1.33 (If G is a planar graph with n ≥ 3 vertices and q edges, then q ≤ 3n − 6. Furthermore, if equality holds,