SOLUTION: My other algebra 2 question is find the value of x. Area of the rectangle=40ft2. xft and (x+3). How do u solve it?

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Question 397939: My other algebra 2 question is find the value of x. Area of the rectangle=40ft2. xft and (x+3). How do u solve it?
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
One side is x ft
The other side is x%2B3 ft
A+=+x%2A%28x%2B3%29
given:
A+=+40 ft2
------------
40+=+x%2A%28x%2B3%29
40+=+x%5E2+%2B+3x
x%5E2+%2B+3x+-+40+=+0
Now you can use the quadratic formula:
x+=+%28-b+%2B-+sqrt%28+b%5E2-4%2Aa%2Ac+%29%29%2F%282%2Aa%29+
a++=1
b+=+3
c+=+-40
x+=+%28-3+%2B-+sqrt%28+3%5E2-4%2A1%2A%28-40%29+%29%29%2F%282%2A1%29+
x+=+%28-3+%2B-+sqrt%28+9+%2B+160+%29%29%2F2+
x+=+%28-3+%2B-+sqrt%28+169+%29%29%2F2+
x+=+%28-3+%2B+13%29%2F2
x+=+5 ft answer
and
x+=+%28-3+-+13%29%2F2
x+=+-8 (can't use the negative root)
also,
x+%2B+3+=+8
A+=+5%2A8
A+=+40 ft2