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30 September, 11:33

Solve for x.

The length of a rectangle is equal to 2 times the width plus 3 feet. If the area of the rectangle is 20 square feet, what are the dimension of the rectangle?

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Answers (2)
  1. 30 September, 11:53
    0
    L*w=20, so l=20/w

    l=2w+3

    20/w=2w+3

    20=2w^2+3w

    2w^2+3w-20=0

    Slip and slide

    w^2+3w-40

    (w+8) (w-5)

    (w+8/2) (w-5/2)

    (w+4) (2w-5)

    w = - 4 or 5/2, but since width must be positive, it is 5/2

    (5/2) * l=20

    l=8

    Final answer: Length = 8, Width = 5/2
  2. 30 September, 11:54
    0
    Let width be x feet

    then the length = 2x + 3 feet

    then the area = x (2x + 3) = 20

    2x^2 + 3x - 20 = 0

    (2x - 5) (x + 4) = 0

    x = 2.5 or - 4 (ignore the negative value)

    so the deimnasions are width = 2.5 feet and length = 2 (2.5) + 3 = 8 feet
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