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Thread: Math Help

  1. #1
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    Question Math Help

    I have a review sheet in math for the final, and one of the questions says to find the answer to the quadratic equation all three ways. The three ways are quadratic formula (I did), factoring (I did), and completing the square, does anyone know how to do "Completing the square" method, I forgot how and didn't bring my text book home, if anyone can help that'd be great and I'd rep+. If it'd help to have a problem it's: X^2+5x+6=0, if you don't wanna give me the answer but just show me, that's fine, I just need help, and besides I already did that equation two other ways anyway .

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    Default

    Ok.
    Completing the square is just like solving for x straight up.
    To do this simply follow the steps...

    Step One:

    X^2+5x+6=0

    Step Two:
    Bring the number without an x value to the other side.

    X^2+5x=-6

    Step Three:
    Take half of the x value, and square that, adding it to both sides.

    X^2+5x+6.25=-6+6.25

    Step Four:
    Turn the Left side into its square.

    (X+5)^2=0.25

    Step Five:
    Take the square root of both sides.

    X+5=(plus or minus)0.5

    Step Six:
    Complete the equation, and get both of the x values.

    X=-5+0.5 and -5-0.5
    X=-4.5 and -5.5

    EDIT: I just realized I did something wrong. I'm totally sure that's how you do it though. the X-intercepts should be -2 and -3...
    EDIT2: I'm really sorry but I don't have the time to fix it...
    Last edited by Runaway; 06-03-2009 at 10:34 AM.

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    Default

    x^2 + 5x + 6 = 0
    x^2 + 5x = -6
    (5/2)^2 = (2.5)^2 = 6.25
    x^2 + 5x + 6.25 = 0.25
    (x + 2.5)^2 = 0.25
    x + 2.5 = 0.5 and x + 2.5 = -0.5
    x = -2 and x = -3

    See this page for more information.
    :-)

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    it's ok Runaway, you just forgot to factor x^2+5x+6.25 and instead you dropped the x in 5x and made it (x+5)^2 instead of (x+2.5)^2 by factoring, still would've helped if I would've saw your post before going to IRC, and Method, while doing my review sheet for my math essay finals, I saw that site for other problems I just wasn't understanding the websites way of showing it, thanks for the help but I went into IRC after posting thread and Nava helped, but you got the right answer and show it nicely, just if I didn't know how to do it now, I probably wouldn't of understood your 3rd line, but thanks for help, you both were repped, please noone else post on here.

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    Default

    X^2+5x+6=0
    (x+3)(x+2)=0
    x+3=0 OR x+2=0
    -3 -3 -2 -2
    x=-3 OR x=-2

    EDIT: sorry for posting here, just this is the easiest way :P

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