Question 817659: Set up an equation and solve: the area of a rectangle is 40 square feet. the length is 2 feet less than twice the width. find the dimensions.
Answer by TimothyLamb(4379)   (Show Source):
You can put this solution on YOUR website! Lw = 40
L = 2w - 2
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Lw = 40
(2w - 2)w = 40
2w^2 - 2w - 40 = 0
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the above quadratic equation is in standard form, with a=2, b=-2, and c=-40
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to solve the quadratic equation, plug this:
2 -2 -40
into this: https://sooeet.com/math/quadratic-equation-solver.php
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the roots of the quadratic are:
w = 5
w = -4
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negative width doesn't make sense for this problem, so use the positive root:
w = 5
L = 8
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Answer:
the speed of a train: 72 km / 1.5 hours = 48 kph
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