Question

The equation D=žn(n-3) gives the number of diagonals D for a polygon with n sides. Use this equation to find the number of diagonals for a palygon that has 6 sides.

Answer 1

$9$

1) Considering that the formula for the number of diagonals of a polygon is:

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

2) And the question tells us that we need to find the number of diagonals for a polygon that has 6 sides, we can plug into that n=6 and solve it this way:

$\begin{gathered} D=\frac{6(6-3)}{2} \\ D=\frac{6\left(3\right)}{2}=\frac{18}{2} \\ D=9 \end{gathered}$