SOLUTION: The length of a rectangle is 4 cm less than twice it's width. Find the length and the width given the area is 70 cm^2.
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Question 848222: The length of a rectangle is 4 cm less than twice it's width. Find the length and the width given the area is 70 cm^2.
Answer by jim_thompson5910(35256) (Show Source): You can put this solution on YOUR website!
The length of a rectangle is 4 cm less than twice it's width. Find the length and the width given the area is 70 cm^2.
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Let x = width
"The length of a rectangle is 4 cm less than twice it's width" ----> Length = 2x - 4
Area = Length * Width
70 = (2x-4) * x
70 = x(2x-4)
70 = 2x^2-4x
0 = 2x^2-4x - 70
2x^2 - 4x - 70 = 0
2(x^2 - 2x - 35) = 0
x^2 - 2x - 35 = 0/2
x^2 - 2x - 35 = 0
(x - 7)(x + 5) = 0
x - 7 = 0 or x + 5 = 0
x = 7 or x = -5
Toss the negative result. You can't have a negative width.
The width is 7 cm
Width = x = 7
Length = 2x - 4
Length = 2(7) - 4 ... plug in x = 7
Length = 14 - 4
Length = 10
The length is 10 cm
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