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"A rectangle has length 2x+4, and width x+3. If the area of this rectangle is 144m^2, calculate the perimeter.

Alright, the question is, "A rectangle has length 2x+4, and width x+3. If the area of this rectangle is 144m^2, calculate the perimeter. be sure to draw a sketch." I know it may seem simple, but I've been doing loads of math problems and my brain is a little dizzy, Thanks for any help :)

Update:

Thanks guys, all of you had the exact same answer, which is right of course. Now it seems very clear to me how to work at this, thanks a bunch to all of you :)

7 Answers

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  • Anonymous
    1 decade ago
    Favorite Answer

    (2x+4)(x+3)=144 ==> 2x^2+10x+12=144

    2x^2+10x-132=0 ==> x^2+5x-66=0

    Factoring results in

    (x+11)(x-6) with x=-11,6

    Since we can't have negative distances, x=6 and the length is 16 and the width is 9

    Perimeter=50

  • 5 years ago

    Simple! For the perimeter, you need to add up all four sides. Two lengths of 4 1/2 yards, two widths of 3 yards: 4 1/2 + 4 1/2 + 3 + 3 = 15 For the area, use the formula for a rectangle, Area = Length x Height: 4 1/2 x 3 = 13 1/2

  • 1 decade ago

    (2x + 4)(x + 3) = 144 ==> 2x^2 + 10x + 12 = 144

    x^2 + 5x + 6 = 72 ===> x^2 + 5x - 66 = 0

    (x + 11)(x - 6) = 0 ==>x = -11 or x = 6

    x = 6

    2x + 4 = 16

    x + 3 = 9

    Perimeter of rectangle = 2[(2x + 4) + ( x + 3)] = 2(3x + 7) =

    2(18 + 7) = 2(25) = 50 meters

    I am sorry but I am unable to sketch. I am sure that you can sketch the rectangle with the aforementioned dimensions.

  • Twiggy
    Lv 7
    1 decade ago

    The area is (2x+ 4)(x + 3)

    = 2x^2 + 10x + 12, so

    2x^2 + 10x + 12 = 144, so

    2x^2 + 10x - 132 = 0, so

    x^2 + 5x - 66 = 0, so

    (x + 11)(x - 6) = 0, so

    x = -11, or x = 6.

    x = -11 is not possible, so x = 6,and

    the length, 2x + 4 = 16,

    the width, x + 3 = 9.

    Check: 9 x 16 = 144.

    The perimeter then is:

    9 + 9 + 16 + 16 = 50.

    Hope this helps, Twiggy.

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  • Anonymous
    1 decade ago

    LW = A

    (2x + 4)(x + 3) = 144

    2x^2 + 6x + 4x + 12 = 144

    2x^2 + 10x - 132 = 0

    x^2 + 5x - 66 = 0

    (x - 6)(x + 11) = 0

    x = 6, - 11 {discard negative root}

    L = 2x + 4 = 12 + 4 = 16

    W = x + 3 = 6 + 3 = 9

    P = 2L + 2W = 32 + 18 = 50

    check

    16(9) = 144

  • 1 decade ago

    A = (2x+4)(x+3) = 2x²+10x+12

    144= 2x²+10x+12

    0=x²+5x-66

    0= (x+11)(x-6)

    x=-11 (not possible)

    x=6

    length = 16

    width = 9

    Perimeter = 50

  • Como
    Lv 7
    1 decade ago

    (2x + 4) (x + 3) = 144

    2x² + 10x + 12 = 144

    x² + 5x + 6 = 72

    x² + 5x - 66 = 0

    (x + 11) (x - 6) = 0

    x = 6 is acceptable

    L = 16 m

    W = 9 m

    P = 50 m

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