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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 :)
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
- Anonymous1 decade agoFavorite 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.
- TwiggyLv 71 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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- Anonymous1 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
- chasrmckLv 61 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
- ComoLv 71 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