A farmer plans to fence a rectangular pasture near a river. The pasture must have 180,000 m^2 in order to provide enough grass for the herd. What dimensions would require the least amount of fencing if no fencing is needed along the river.
Along the river there is no measurement. Two sides are x and and the third side is (180,000-2x).
Area of rectangle is length times width.
A = x(180,000-2x)
A prime = 180,000-4x.
I then set A prime to 0 to find my critical point.
I found x to be 45,000 but this makes no sense. The correct answer is 600 meters by 300 meters. What am I doing wrong?