posted by Leian .
Mary wants to build a fence around a rectangular area for a garden. She has 150 ft of fencing and she wants to leave 10 ft opening on side for a gate. In order to make a area of the garden. A maximum what should the dimensions of the garden will be?
2x+2y-10 = 150
x+y = 80
area = xy = x(80-x)
Just find the vertex of that parabola for maximum area.