completing the square: x^2 - 6x + 2 = 0

[lil1ch1ck]

This was on my latest math test for a tutoring class. I know I've gotten the wrong answer since we went over the test in class, but I was unable to copy down the correct answer before the teacher erased the board.

Can someone explain to me how to complete the square on this?

. . .x^2 - 6x + 2 = 0

Am I supposed to move the 2 to the other side of the equation first, before adding half of the coefficient that's squared? I hope that question makes sense.

 

[galactus]

Yes, move the 2.

\(\displaystyle \L\\x^{2}-6x=-2\)

Half the coefficient:

\(\displaystyle \L\\x^{2}-6x+9=-2+9\)

Factor:

\(\displaystyle \L\\(x-3)^{2}-7\)

 

[wantedcriminal03]

X^2-6x+2=0

You do (x-half the coefficient of x)^2 - the coeffecient of x^2 +2 = 0

so (x-3)^2 - 3^2 +2=0
so (x-3)^2 - 9 + 2=0
so (x-3)^2 = 7
so x-3 = +/- sqrt 7
x = 3 +/- sqrt 7