Answer: 5 feet
Step-by-step explanation: To find the width of the rectangle,
start with the formula for the perimeter, shown below.
Perimeter = 2l + 2w
Since we know the perimeter is 36 and the
length is 13, we have 36 = 2(13) + 2w.
Simplifying on the right, we have 36 = 26 + 2w.
Not subtract 26 from both sides to get 10 = 2w.
Now divide both sides by 2 and 5 = w.
So the with is 5 feet.
Answer:
x = 28 m
y = 14 m
A(max) = 392 m²
Step-by-step explanation:
Rectangular garden A (r ) = x * y
Let´s call x the side of the rectangle to be constructed with a rock wall, then only one x side of the rectangle will be fencing with wire.
the perimeter of the rectangle is p = 2*x + 2*y ( but in this particular case only one side x will be fencing with wire
56 = x + 2*y 56 - 2*y = x
A(r) = ( 56 - 2*y ) * y
A(y ) = 56*y - 2*y²
Tacking derivatives on both sides of the equation we get:
A´(y ) = 56 - 4 * y A´(y) = 0 56 - 4*y = 0 4*y = 56
y = 14 m
and x = 56 - 2*y = 56 - 28 = 28 m
Then dimensions of the garden:
x = 28 m
y = 14 m
A(max) = 392 m²
How do we know that the area we found is a local maximum??
We find the second derivative
A´´(y) = - 4 A´´(y) < 0 then the function A(y) has a local maximum at y = 14 m
Answer:
(15, −4)
Step-by-step explanation:
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