Answer:
Step-by-step explanation:
If x is the width of the field in the direction perpendicular to the river, then 2000-2x is the length along the river. The total area is ...
x(2000 -2x) = 500000
x^2 -1000x +250000 = 0 . . . . . rearrange to standard form
(x -500)^2 = 0 . . . . . . . . . . . . . . . factor
x = 500 . . . . one solution
The field is 1000 meters long (along the river) and 500 meters wide.