Respuesta :
Answer:
a) Function A(x) = (60*x - 1/2*x²)
b)Side length x = 60 m the other side y = 30 m
c) A (max) = 1800 m²
Step-by-step explanation:
Area of rectangular garden with length " x " and wide "y"
A = x*y
Perimeter of rectangular area ( only three sides 2*y and 1*x)
P(r) = 2*y + x
P(r) = 120 = 2*y + x
y = ( 120 - x ) /2
Area of the garden as function of x is
A(x) = [( 120 - x ) /2]*x ⇒ A(x) = (60*x - 1/2*x²)
Taking derivatives on both sides of the equation:
A´(x) = 60 - x
A´(x) = 0 60 - x = 0
x = 60 m
Then
y = ( 120 - x ) / 2 ⇒ y = (120 - 60 )/2
y = 30 m
A(max) = 30 * 60
A(max) = 1800 m²
The side length (x) is 30 m each
The maximum area is 1800 m².
He has 120 meters for fencing . He use it to form 3 sides of a rectangular garden.
Therefore,
let
the side parallel to the house = y
the sides perpendicular to the house = x (2 sides)
Therefore,
perimeter = 2x + y
120 = 2x + y
y = 120 - 2x
area = x(120 - 2x)
area = 120x - 2x²
area = -2x² + 120x
The leading coefficient is less than zero, therefore, the parabola is facing downward. The maximum area is at (h, k).
where
h = - b / 2a
a = -2
b = 120
h = - 120 / 2 × -2
h = 120 / 4 = 30
The sides perpendicular to the building = 30 meter
The side parallel to the building = 120 - 2(30) = 60 meters
The maximum area = 60 × 30 = 1800 m²
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