Answer:
The maximum possible area of the pasture = 2450 square feet
Step-by-step explanation:
Let the length of the creek be 'L'
and, the width of the rectangular area be 'B'
Data provided:
The rectangular area is enclosed using the creek as one side and fencing for the other three sides
Thus, 2B + L = 140 feet
or
L = 140 - 2B .........(1)
Now,
Area of the rectangular land, A = L × B
using (1)
A = ( 140 - 2B) × B
or
A = 140B - 2B²
Now to maximize the area, differentiating the area with respect to width 'B'
we have
= 140 - 2 × 2 × B ...........(2)
for point of maxima or minima , = 0
thus,
140 - 2 × 2 × B = 0
or
4B = 140
or
B = 35 feet
differentiating (2) with respect to B, for verifying the maxima or minima
= 0 - 2 × 2 = -4
since, is negative,
therefore,
B = 35 feet is point of maxima
from (1)
L = 140 - 2B
or
L = 140 - 2 × 35
or
L = 140 - 70 = 70 feet
Hence,
The maximum possible area of the pasture = L × B
= 70 × 35
= 2450 square feet