Jenny has 280 meters of fencing and wishes to form three sides of a rectangular field. the fourth side borders a river and will not need fencing. as shown below, one of the sides has length x (in meters). find a function that gives the area a(x) of the field in terms of x

a(x) = x*y = x*(280 - 2x) square meters

Step-by-step explanation:

In the figure attached, a plot of the problem is shown. Let's call y the length of the side that parallels the river

The perimeter that the fence cover is:

2x + y =  280 meters

Isolating y:

y =  280 meters - 2x

The area of the field is:

a(x) = x*y = x*(280 - 2x) square meters

15.5

step-by-step explanation:

5

∑

n = 1

substitute n = 1, 2, 3, 4, 5 and sum the terms

= + + + 2² + 2³

= 0.5 + 1 + 2 + 4 + 8

= 15.5