# Planar graph proof [duplicate]

I need to prove some graph problem.

Let G be planar graph with more than 10 vertices. I need to prove the its complement graph G' is not planar.

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## marked as duplicate by Paul, Douglas S. Stones, draks ..., Chris Eagle, MJDSep 27 '12 at 6:20

Hint: Try to show that $G'$ contains a full subgraph of 5 vertices $K_5$ or the full bipartite graph $K_{3,3}$.