SOLUTION: using the word problem that i am given (below) i am supposed to wirte a quadratic equation to model the problem. i have never been good at word problems so i though i would try thi

Algebra ->  Algebra  -> Quadratic Equations and Parabolas -> SOLUTION: using the word problem that i am given (below) i am supposed to wirte a quadratic equation to model the problem. i have never been good at word problems so i though i would try thi      Log On

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Question 523883: using the word problem that i am given (below) i am supposed to wirte a quadratic equation to model the problem. i have never been good at word problems so i though i would try this. thanks for your help in advance.
26. Brian wants to increase the size of his 3 feet by 6 feet garden. he wants to increase each side by the same amount to double the area. find the amount by which he should increase each side. round to the nearest tenth.
I tried to do proportion and found that (obviously) double 3/6 is 6/12 but i wasnt sure if that was even relevant to the question. I also know that quadratic formula is ex:3x^2+2x+5=0 Please help!
Answer by ankor@dixie-net.com(15653) About Me  (Show Source):
You can put this solution on YOUR website!
Brian wants to increase the size of his 3 feet by 6 feet garden.
he wants to increase each side by the same amount to double the area.
find the amount by which he should increase each side. round to the nearest tenth.
Find the area: 3*6 = 18, double the area = 36 sq/ft
:
Let x = amt to be added to the length and width to double the area
(x+3)*(x+6) = 36
FOIL
x^2 + 6x + 3x + 18 = 36
x^2 + 9x + 18 - 36 = 0
x^2 + 9x - 18 = 0. the quadratic equation for this
Use the quadratic formula
x+=+%28-b+%2B-+sqrt%28+b%5E2-4%2Aa%2Ac+%29%29%2F%282%2Aa%29+
where a=1, b=9, c=-18
x+=+%28-9+%2B-+sqrt%289%5E2-4%2Aa%2A-18+%29%29%2F%282%2A1%29+
:
x+=+%28-9+%2B-+sqrt%2881-%28-72%29+%29%29%2F2+
:
x+=+%28-9+%2B-+sqrt%28153+%29%29%2F2+
The positive solution
x+=+%28-9+%2B+12.37%29%2F2+
x = 3.37%2F2
x = 1.7 ft added to each dimension
:
:
See if that works: 4.7 * 7.7 = 36.19 ~ 36 sq/ft