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Am I missing something?

  1. Oct 26, 2011 #1
    For our typical quadratic equation:

    x= (-b± [itex]\sqrt{b^2-4ac}[/itex])/2a

    Am I missing something? I mean the value underneath the square root turns out to be a negative number, so technically this equation would not have worked right? It's from a textbook by the way. This is actually an analytical chemistry application question.

    x= -6.8*10-4 ± [(6.8*10-4)2 - (4)(6.8*10-4)]0.5/(2)(1)
  2. jcsd
  3. Oct 26, 2011 #2


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    Homework Helper

    The equation works fine with negative numbers. Sometimes this happens when the roots should be real, either a mistake was made or the situation modeled is impossible or there was rounding and the roots returned are barely complex and should be rounded back to real.
  4. Oct 26, 2011 #3
    is b = c ?
    or did you write the wrong value?

    In any case, negative ARE possible and you go into complex number territory
  5. Oct 26, 2011 #4


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    Gold Member

    If a proper math equation (which this is) is applied in a way that doesn't give a physically possible answer, that's not the math's fault and you need to look at whether or not the right numbers have been put in or whether perhaps the equation is not the right one to use in a given situation.
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