The conditions under which the Farmer Jack should build his fence is; B. The length of the fence must be greater than or equal to 15 ft. or less than or equal to 7 ft.
We are told that the length of the entire fence is 44 ft long. Thus it means that the perimeter is 44 ft long.
Now, since the fence is a rectangular shape, it means that;
a + b = 44/2
a + b = 22 ----(1)
Now, we are told that the area has to be greater than 105 sq. ft. Thus;
ab > 105 ------(2)
From eq 2; a > 105/b
Thus; (105/b) + b = 22
Multiply through by b to get;
105 + b² = 22b
b² - 22b + 105 = 0
Solving using quadratic equation calculator gives;
b ≤ 7 or b ≥ 15
Thus, we can conclude that the length of the fence must be greater than or equal to 15 ft. or less than or equal to 7 ft.
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