Track / Stage 4 / 65 of 340 #325 of 2000

If we double the number of sides in a polygon, the number of diagonals increases by 45. Which polygon is this?

This one wants a proof. Work it on paper, read the official solution, then mark yourself honestly — the ladder only means something if the record is true.

I solved it I didn't Skip

Official solution

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Source: NuminaMath-1.5, licensed Apache-2.0. Statement and solution reproduced as published; topic, difficulty and ordering added by this site.