Solve a Quick Math Question: How Many Sides in a Polygon w/ 119 Diagonals?

[get_rekd]

d=n^2 - 3n / 2

where d = number of diagonals
and n = the number of sides of the polygon.

A polygon has 119 diagonals, how many sides does it have?

119 = n^2 - 3n / 2

I am not sure how to do this? can someone please help?

sorry this isn't physics related

 

[Bill Foster]

An n-sided polygon has this many diagonals:

$$\frac{n(n-3)}{2}$$

Solve for $$n$$.

 

[AKG]

d=n^2 - 3n / 2

where d = number of diagonals
and n = the number of sides of the polygon.

A polygon has 119 diagonals, how many sides does it have?

119 = n^2 - 3n / 2

I am not sure how to do this? can someone please help?

sorry this isn't physics related

Quadratic Formula