Question 823794: [ The area of a rectangle is 440 square centimeters; The perimeter is 84 centimeters. Find the length and width. ]
Answer by TimothyLamb(4379)   (Show Source):
You can put this solution on YOUR website! ---
a = xy = 440
p = 2x + 2y = 84
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2y = 84 - 2x
y = (84 - 2x)/2
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xy = 440
x(84 - 2x)/2 = 440
x(42 - x) = 440
42x - xx = 440
-xx + 42x - 440 = 0
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the above quadratic equation is in standard form, with a=-1, b=42, and c=-440
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to solve the quadratic equation, by using the quadratic formula, copy and paste this:
-1 42 -440
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this quadratic has two real roots (the x-intercepts), which are:
x = 20
x = 22
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answer:
length = 22 cm
width = 20 cm
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