SOLUTION: Solve by completing the square. 2x^2-12x-18=0 How do you do it. Thanks

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Question 66792: Solve by completing the square.
2x^2-12x-18=0
How do you do it. Thanks
Found 2 solutions by Earlsdon, ptaylor:
Answer by Earlsdon(6294) About Me  (Show Source):
You can put this solution on YOUR website!
Solve by completing the square:
2x%5E2-12x-18+=+0 First, you want to get the coefficient of the x%5E2 term to be 1, so divide everything by 2.
%282x%5E2-12x-18%29%2F2+=+0%2F2 Simplify.
x%5E2-6x-9+=+0 Now move the constant term (-9) to the right side of the equation by adding 9 to both sides.
x%5E2-6x+=+9 Next, add the square of half the x-coefficient %28%28-6%29%2F2%29%5E2+=+%28-3%29%5E2 = 9 to both sides.
x%5E2-6x%2B9+=+18 Now factor the left side.
%28x-3%29%5E2+=+18 Take the square root of both sides.
x-3+ = +/-sqrt%2818%29 Add 3 to both sides.
x+=+3%2B-sqrt%2818%29 Simplify. Note that: sqrt%2818%29+=+sqrt%289%2A2%29 = 3sqrt%282%29
x1+=+3%2B3sqrt%282%29
x2+=+3-3sqrt%282%29

Answer by ptaylor(2198) About Me  (Show Source):
You can put this solution on YOUR website!
Solve by completing the square.
2x^2-12x-18=0
How do you do it. Thanks
2x^2-12x-18=0 This is in standard form with A=2, B=-12 and C=-18.
First, divide each term by 2; (we want A to equal 1) and we get:
x^2-6x-9=0 now add 9 to both sides (we are setting up the left side so we can complete the square) and we have:
x^2-6x+9-9=9
x^2-6x=9 Now we will complete the square on the left side. In other words, we will select a C for the left side that results in the left side being a perfect square. When A=1, we can take half B , square it, and add it to both sides. We will now have a perfect square on the left side. Another way to look at it is: when A=1, then B is the sum of the factors of C. Here, we are choosing the factors of C that results in a perfect square and this will work in most every case.
(1/2)B=-3 squaring it, we get 9. So we add 9 to both sides
x^2-6x+9=18
(x-3)^2=18 take the square root of both sides
x-3=+or-sqrt(18)=+or-sqrt(9)(2)
x=3+3sqrt(2)=3(1+sqrt(2))
x=3-3sqrt(2)=3(1-sqrt(2))
Ck by using the quadratic formula
Hope this helps---ptaylor