Once you attempt the question then PrepInsta explanation will be displayed.
Number of diagonal in a polygon = \frac{n\times (n-3)}{2}, where n is number of sides
Thus, \frac{n\times (n-3)}{2}= 77
= > n^{2} – 3n = 154
= > n^{2} – 3n – 154 = 0
= > n^{2} -14n + 11n – 154 = 0
= > n(n-14) + 11(n-14) = 0
= > (n-14) (n+11) = 0
n = 14 & n = -11
Since, the side can’t be negative. So, n = -11 is rejected.
Hence the number of sides of the polygon is 14
Video Explanation:
Login/Signup to comment