SOLUTION: The area of a rectangle is 64cm squared. What are the dimensions if the perimeter is a minimum?

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Question 1078547: The area of a rectangle is 64cm squared. What are the dimensions if the perimeter is a minimum?
Answer by Boreal(15235) About Me  (Show Source):
You can put this solution on YOUR website!
length is x
width is y
xy=64 cm^2
y=64/x
perimeter is 2x+2y=2x+128/x
That has to be a minimum
derivative of that is 2-128/x^2
Set that equal to 0
128/x^2=2
2x^2=128
x=8 cm
y=8 cm
It is a square, and the perimeter is a minimum of 32 cm.