SOLUTION: solve by completing the square 3/8x^2 = 1/8 - x Get 0 on one side: 3/8x^2 + x - 1/8 = 0 Divide both sides by 8 and then you get: 3x^2+8x-1 =0 Then I make the coefficient of x^2

Algebra ->  Quadratic Equations and Parabolas -> SOLUTION: solve by completing the square 3/8x^2 = 1/8 - x Get 0 on one side: 3/8x^2 + x - 1/8 = 0 Divide both sides by 8 and then you get: 3x^2+8x-1 =0 Then I make the coefficient of x^2      Log On


   

Question 293255: solve by completing the square 3/8x^2 = 1/8 - x
Get 0 on one side: 3/8x^2 + x - 1/8 = 0
Divide both sides by 8 and then you get: 3x^2+8x-1 =0
Then I make the coefficient of x^2 equal to 1, I divide both sides by 3, term by term.
Then I get x^2 + 8/3 - 1/3 = 0
This is where I get confused. I need help completing the square now. I know I square 1/2(8/3)^2 and that gives me a square and I add 16/9 to both sides.





Found 3 solutions by Alan3354, Earlsdon, richwmiller:
Answer by Alan3354(69443) About Me  (Show Source):
You can put this solution on YOUR website!
solve by completing the square 3/8x^2 = 1/8 - x
Get 0 on one side: 3/8x^2 + x - 1/8 = 0
Divide both sides by 8 and then you get: 3x^2+8x-1 =0 *** Actually, you multiplied by 8, but good work.
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Then I make the coefficient of x^2 equal to 1, I divide both sides by 3, term by term.
Then I get x^2 + 8/3 - 1/3 = 0 *** 8x/3
This is where I get confused. I need help completing the square now. I know I square 1/2(8/3)^2 and thaat gives me a square and I add 16/9 to both sides.
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x^2 + 8x/3 - 1/3 = 0
x%5E2+%2B+%288%2F3%29x+=+1%2F3 Move the coefficient to the right side
Then add ((8/3)/2)^2 to both sides
x%5E2+%2B+%288%2F3%29x+%2B+16%2F9+=+1%2F3+%2B+16%2F9
%28x+%2B+8%2F3%29%5E2+=+25%2F9
Can you take it from there?

Answer by Earlsdon(6294) About Me  (Show Source):
You can put this solution on YOUR website!
Solve by compleing the square:
%283%2F8%29x%5E2+=+%281%2F8%29-x Get into standard form.
%283%2F8%29x%5E2%2Bx-1%2F8+=+0 Multiply both sides by %288%2F3%29
x%5E2%2B%288%2F3%29x-1%2F3+=+0 Add 1%2F3 to both sides.
x%5E2%2B%288%2F3%29x+=+1%2F3 Now complete the square by adding the square of half the coefficient of the x-term. %28%281%2F2%29%288%2F3%29%29%5E2+=+16%2F9 to both sides.
x%5E2%2B%288%2F3%29x%2B16%2F9+=+%281%2F3%29%2B%2816%2F9%29 Simplify.
%28x%2B%284%2F3%29%29%5E2+=+19%2F9 Take the square root of both sides.
x%2B%284%2F3%29+=+sqrt%2819%29%2F3 or x%2B%284%2F3%29+=+-sqrt%2819%29%2F3 Subtract 4%2F3 from both sides.
x+=+-%284%2F3%29+%2B+sqrt%2819%29%2F3 or -%284%2F3%29-sqrt%2819%29%2F3
x+=+%28-4-sqrt%2819%29%29%2F3 or %28-4-sqrt%2819%29%29%2F3

Answer by richwmiller(17219) About Me  (Show Source):
You can put this solution on YOUR website!
You did it correctly but you explained it wrong.
"Divide both sides by 8 and then you get"
You didn't divide, you actually multiplied.
You didn't really do this 1/2(8/3)^2
You really did this (4/3)^2 or (8/3*1/2)^2 which equals 16/9.
And you don't end up with x^2 + 8/3 - 1/3 = 0 but x^2 + 8x/3 - 1/3 = 0
You forgot the x in the x term
BTW We didn't really need to get it equal to 0
x^2 + 8x/3 = 1/3
So now we add 16/9
x^2 + 8x/3+16/9 = 1/3 +16/9
x^2 + 8x/3+16/9 = 3/9 +16/9
x^2 + 8x/3+16/9 = 19/9
(x+4/3)^2=19/9
x=-4/3+-sqrt(19/9)
x=-4/3+-sqrt(19/9)
x=1/3(-4-sqrt(19))
x=1/3(-4+sqrt(19))