What is the formula for finding the area of a regular polygon work perimeter p and apothem length a?

What is the 9th term in the geometric sequence described by this explicit formula? an=-6. (2)(n-1) apex

50 plz, given the system of equations, match the following items. x + 3 y = 5 x - 3 y = -1 a) x-determinant b) y-determinant c) system determinant match the following to the pictures below.

Math i have no idea how to do a and b