maths

圖片參考：http://i132.photobucket.com/albums/q40/cindycsy101/maths-1.jpg


Let BC=AD=x m and CD=y m

BC+CD+AD=200=>2x+y=200...(*)

The area
=xy
=x(200-2x)
=-2x^2+200x
=-2(x^2-100x)
=-2(x^2-100x+50^2-50^2)
=-2(x-50)^2+5000

So, when x=50, the area is maximized.
Hence, the dimension is 100m*50m