SOLUTION: The length of a rectangle is 7 centimeters less than twice its width. Its area is 30 square centimeters. Find the dimension of the rectangle.

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Question 211465This question is from textbook Beginning & Intermediate Algebra
: The length of a rectangle is 7 centimeters less than twice its width. Its area is 30 square centimeters. Find the dimension of the rectangle. This question is from textbook Beginning & Intermediate Algebra

Answer by RAY100(1637) About Me  (Show Source):
You can put this solution on YOUR website!
Area = Length * Width
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but L= 2w-7
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A= (2w-7)*w = 2w^2 -7w also = 30,,,,,given
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2w^2 -7w -30 =0
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solve using quadratic formula
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a=2,,,b=-7,,,,,c=-30
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w=[-(-7) +/- sqrt{(-7)^2-4(2)(-30)}]/2(2)
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w= [ 7 +/- sqrt{49+240}]/4
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w= [ 7 +/-sqrt {289}]/4
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w= [7 +/- 17]/4
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w= 6, -2.5 (not reasonable)
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l=2w-7 = 2*6-7 = 5
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check, A=5*6 =30,,,,,,ok