One hundred meters of fencing is available to inclose a rectangular area next to a river (see figure above). Give a function A that can represent the area that can be enclosed in terms of x.

Answer:
A=2x(-x+50)
Step-by-step explanation:
Since there is a river, you only need to fence 3 sides of the rectangular area.
Let's name x the shorter side of the rectangular area. (height)
Hence, since we have 100 meters of fencing, the longer side of the rectangle would be 100-2x (base)
Area is base*height.
Hence, our equation would be:
A=x(100-2x)
Simplify
A=100x-2x^2
A=2x(-x+50)