Question

A polygon has 35 diagonals, then the number of sides of the polygon is

Answer 1

$here \: is \: your \: ans$
Here
The number of diagonals
= n(n-3)/2
Now
n(n-3)/2 = 35

n(n-3) = 70

n^2 - 3n - 70 = 0, or

(n-10)(n+7) = 0,

n = 10 or n= -7.

so negative number can not be taken so neglect them

n= 10

Hope it's helpful ✌