Pre-Calculus, urgent, please help.

Question

Farmer Ed has 9,500 meters of​ fencing, and wants to enclose a rectangular plot that borders on a river. If Farmer Ed does not fence the side along the​ river, what is the largest area that can be​ enclosed in sq meters?

Answer 1

Perimeter = 9500

2W + L = 9500

L = 9500 - 2W

Area = L•W = (9500 - 2W)(W)

A(W) = -2W² + 9500W

The max will occur at the vertex. The vertex is found at W = -b/(2a) = -9500/(2(-2)) = 2375

L = 9500 - 2(2375) = 4750

Max Area = 4750•2375 = 11,281,250 square meters