SOLUTION: Good afteroon. I have a question regarding completing the square. Here is the equation: {{{9x^2-18x=-3}}} I keep coming up with x= 1 plus minus .816 but in class the answer wa

Algebra ->  Quadratic Equations and Parabolas -> SOLUTION: Good afteroon. I have a question regarding completing the square. Here is the equation: {{{9x^2-18x=-3}}} I keep coming up with x= 1 plus minus .816 but in class the answer wa      Log On


   

Question 210452: Good afteroon. I have a question regarding completing the square. Here is the equation: 9x%5E2-18x=-3
I keep coming up with x= 1 plus minus .816 but in class the answer was x=3+square root 6 over 3 and x=3-square root 6 over 3. Does that seem correct? If so I just don't know how it got that way? Any help would be appreciated. :)
Answer by tutor_paul(519) About Me  (Show Source):
You can put this solution on YOUR website!
I am not sure what they are doing in class, but you got it right.
9x%5E2-18x=-3
Divide each term by 9 to get x^2 term to have coefficient of 1:
x%5E2-2x=-1%2F3
Divide coefficient of x by 2 and square. add result to both sides:
x%5E2-2x%2B1=2%2F3
Represent left side as perfect square:
%28x-1%29%5E2=2%2F3
Take square root of each side:
x-1=+-sqrt(2/3)
Solve for x:
x=1+-sqrt(2/3)
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Good Luck,
tutor_paul@yahoo.com