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Homework Help: Factoring with the quadratic formula

  1. Oct 1, 2006 #1
    I have a huge headache and I can't understand why this works... I am reviewing the quadratic formula so that I can solve trig questions, but I am stuck on this one part...

    The point is to factor [tex]x^2+2x-1[/tex]

    I ( and the textbook ) use the quadratic formula to get the roots of it and come up with

    [tex]-1\pm\sqrt{2} [/tex]

    How do I use this to factor into [tex](x+1-\sqrt{2})(x+1+\sqrt{2})[/tex]?

    I remember the quadratic formula as being more useful for solving quadratics where 1 side =0... I don't remember factoring with it! Can someone help? I would try to figure it out on my own but my head is spinning and I am under time pressure at this point. Thanks alot guys.

    I really do appreciate the help that I recieve on these boards. :smile:
    Last edited: Oct 1, 2006
  2. jcsd
  3. Oct 1, 2006 #2


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    The quadratic formula gives you 2 roots r1 and r2 you then get the factors from

    (x - r1) (x - r2) You then need to check your work by multiplying the 2 factors to ensure that you get back your starting quadratic.
  4. Oct 2, 2006 #3
    Thankyou Integral!! You helped me remember :)
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