A farmer has 500 feet of fencing to enclose a rectangular
field. A barn will be used as part of one side of the field
(see figure). Prove that the area of the field is greatest
when the rectangle is a square.
![A farmer has 500 feet of fencing to enclose a rectangular field A barn will be used as part of one side of the field see figure Prove that the area of the field class=](https://us-static.z-dn.net/files/dd3/a74d3dbdba3ae3d5e6b09439307034dc.png)