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11 October, 21:12

A rectangle has a length, 3x+7, and a width of x+5. The area of the rectangle is 128 square inches. What is the length of the rectangle in inches?

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  1. 11 October, 23:28
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    First, we know the formula for area is:

    Area = Length * Width

    Therefore, 128 = (3x+7) (x+5)

    We can use the F. O. I. L method to multiply

    - First: (3x * x) = 3x²

    -Outer: (3x*5) = 15x

    -Inner: (7*x) = 7x

    -Last: (7*5) = 35

    Now we add the sum → 3x² + 15x + 7x + 35 → 3x² + 22x + 35

    3x² + 22x + 35 = 128

    3x² + 22x - 93 = 0

    Now you have to factor to solve for the x value.

    (3x + 31) (x-3)

    x = 3 & x = - 31/3

    The negative value is eliminated because u can't have a negative length.

    The length is 3x+7

    L = 3 (3) + 7

    L = 9+7

    L = 16
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