math problem #3a farmer has 600 ft of fence and wants to sec

if the farmer wants 3 equal rectangular pens,then each pen would be made by 200 ft of fence.suppose that the length connect to the barn is x ft,then the other sides of the rectangle have the identical length of (200-x)/2 ft.hence the pen area is S=x(200-x)/2,when x=100ft S has the maximum value that is 5000 sqrft
the length of each side are 100ft 50ft 50ft

尺寸是长100,两边宽50...因为600ft做3 equal rectangular pens, 所以每个用料200ft.(200是三边的周长)拿其中一个来算:
设其中一边为X(因为有3边,所以必有两边是一样长的).另两边中的一边为0.5(200-X)..面积为y..
y=0.5(200-X)X 当X=100时取得最大值..
所以另一边为50...