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.

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) (Show Source): You can put this solution on YOUR website!
Area = Length * Width
.
but L= 2w-7
.
A= (2w-7)*w = 2w^2 -7w also = 30,,,,,given
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2w^2 -7w -30 =0
.
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)
.
l=2w-7 = 2*6-7 = 5
.
check, A=5*6 =30,,,,,,ok

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