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Math Help - completing the square

  1. #1
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    completing the square

    by completing the square the expression that is x^2+14 x +156 equals (x+A)^2+B

    so the question is what would A and B equal

    this is my last question...i am stumped on a few of these..
    Last edited by mr fantastic; September 18th 2009 at 03:38 PM. Reason: Restored original question and merged with another post (also originally deleted)
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  2. #2
    Super Member redsoxfan325's Avatar
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    Quote Originally Posted by frozenflames View Post
    by completing the square the expression that is x^2+14 x +156 equals (x+A)^2+B

    this is my last question...i am stumped on a few of these..
    I'll put you out of you're misery. Given an equation x^2+bx+c, You want to get something of the form x^2+bx+\left(\frac{b}{2}\right)^2+k, for some constant k. (Note that k+\left(\frac{b}{2}\right)^2=c.) When factored, this will become \left(x+\frac{b}{2}\right)^2+k.

    So in this case, \frac{b}{2}=7 so \left(\frac{b}{2}\right)^2=49.

    Break up the equation: x^2+14x+156=x^2+14x+49+107

    Factor and you're done: x^2+14x+49+107=(x+7)^2+107.

    So A=7 and B=107.

    ---------------------

    EDIT: You've already figured it out I see. Well, at least you have something to check it against now.
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  3. #3
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    thanks a lot, but i figured that one out.
    Last edited by mr fantastic; September 18th 2009 at 03:36 PM. Reason: Moved a question to another thread
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