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3 votes
If a polygon has 189 diagonals how many sides does the polygon have ?

2 Answers

4 votes
(n take 2) minus n = 189
n(n-3)/2 = 189
n(n-3) = 378
n^2-3n-378 = 0
n=21

2 votes
n(n-3)/2=189
n(n-3)=378
n^2-3n-378=0
n=21
answered
User Siavash Alp
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