Fencing question

Question

A farmer has 600 ft of fencing. He wants to create a rectangular section away from the barn for horses.

 a) Help the farmer determine the dimensions that will allow for the maximum area. 

 b) Now that you have the dimensions determine the area of the section. 

Answer 1

w represents the width

600 - 2w represents the length

A(w) = w(600 - 2w)

A(w) = -2w² + 600w

Maximum occurs at w = -600 / 2(-2). What is that?