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Math Help - Quadratic Formula Help

  1. #1
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    Quadratic Formula Help

    Im really not sure if this is calculus and I know this is really simple but this is the one thing that has always confused me so help me out...

    x^2+40x-40=0

    what is x?
    haha thanks
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  2. #2
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    Quote Originally Posted by Gman8990 View Post
    Im really not sure if this is calculus and I know this is really simple but this is the one thing that has always confused me so help me out...

    x^2+40x-40=0

    what is x?
    haha thanks
    It can be written as (x + 20)^2 - 400 - 40 = 0 ....
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  3. #3
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    Quote Originally Posted by Gman8990 View Post
    Im really not sure if this is calculus and I know this is really simple but this is the one thing that has always confused me so help me out...

    x^2+40x-40=0

    what is x?
    haha thanks
    Since you titled this "Quadratic Formula Help", do you know what the quadratic formula is?

    If ax^2+ bx+ c= 0 then

    \frac{-b\pm\sqrt{b^2- 4ac}}{2a}

    Here a= 1, b= 40 and c= -40.

    Of course, mr. fantastic's completing the square works nicely too.
    Last edited by mr fantastic; March 26th 2010 at 02:00 PM. Reason: Fixed latex - you missed a } in the fraction (;
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