# Quadratic equation

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• Dec 2nd 2008, 04:06 PM
I hate Math
Quadratic equation
Ok so i keep getting stuck on these, can someone please explain, because my teacher didn't do a good job at that...lol...oh and this ( 3x^2) means that the 3 is squared...apparently the end result should look like this
( )( ) yes i suppose it is factoring...It says "Solve each quadratic equation by completing the square"

3x^2 = -6x + 9
• Dec 2nd 2008, 04:19 PM
vincisonfire
If I understand well you have
$*9x^2 = -6x + 9$
You first need to complete the square.
Put everything on one side.
$9x^2 + 6x - 9 =0$
Try to make a square out of
$9x^2 + 6x$
Here
$9x^2 + 6x +1 -1 - 9 =(3x+1)^2 -10 =0$
Now you can put the 10 back on one side.
$(3x+1)^2 = 10 \implies \text{ take the square root } 3x+1 = \pm \sqrt{10}$ and solve for x to find
$x = \frac{\pm\sqrt{10}-1}{3}$
• Dec 2nd 2008, 04:19 PM
euclid2
Quote:

Originally Posted by I hate Math
Ok so i keep getting stuck on these, can someone please explain, because my teacher didn't do a good job at that...lol...oh and this ( 3x^2) means that the 3 is squared...apparently the end result should look like this
( )( )

3x^2 = -6x + 9

What do you need to do, factor, graph, etc...?
• Dec 2nd 2008, 04:36 PM
skeeter
$3x^2 = -6x + 9$

$3x^2 + 6x - 9 = 0$

$3(x^2 + 2x - 3) = 0$

$3(x + 3)(x - 1) = 0$

btw ... change the username, it doesn't say good things about your attitude.