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Homework Help: Apply the quadratic formula

  1. Nov 30, 2009 #1
    Applying it to

    -x2 - bx +c = 0

    I would have thought it to be

    (b +- (b2+4c)0.5) /-2

    = (-b +- (b2+4c)0.5) /2


    Anytime I try and graph a function like it the roots are

    (b +- (b2+4c)0.5) /2

    I can't see why this is?

  2. jcsd
  3. Nov 30, 2009 #2


    Staff: Mentor

    Yes, the roots of the equation above are x = (-b +- (b2+4c)0.5) /2.
    I can't either, but I suspect you're doing some unconscious sign-changing of the coefficients when you enter the function into whatever graphing utility you're using.

    Regarding your first equation, why don't you multiply both sides by -1 to get x^2 + bx - c = 0? The solutions would be the same.
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