Question 300563
Find the dimensions of a rectangular lawn whose perimeter is 100 feet and whose area is 600 square feet. 
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Let x = length
and y = width
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2(x+y) = 100  (equation 1)
xy = 600   (equation 2)
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Solve equation 2 for y:
xy = 600
y = 600/x
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Substitute the above into equation 1 and solve for x:
2(x+y) = 100
2(x+600/x) = 100
x+600/x = 50
x^2+600 = 50x
x^2-50x+600 = 0
(x-20)(x-30) = 0
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x = {20,30}
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Dimensions are 20 feet by 30 feet