Answer:
781250
Step-by-step explanation:
Let x = length of fenced side parallel to the side that borders the river
and y = length of each of the other two fenced sides
Then, x + 2y = 2500
<=> x = 2500- 2y
Area = xy = y(2500-2y)
= - + 2500y
The graph of the area function is a parabola opening downward.
The maximum area occurs when y = -2500/[2(-2)] = 625
x = 2500-2y = 1250
The maximum area that can be enclosed = xy = 1250*625 = 781250