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Math Help - Quadratic equation

  1. #1
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    Exclamation 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
    Last edited by I hate Math; December 2nd 2008 at 03:27 PM.
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  2. #2
    Senior Member vincisonfire's Avatar
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    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}
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  3. #3
    Senior Member euclid2's Avatar
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    Quote Originally Posted by I hate Math View Post
    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...?
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  4. #4
    MHF Contributor
    skeeter's Avatar
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    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.
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