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Homework Help: Using quadratic formulae

  1. Jul 23, 2009 #1
    hey guys, could u use the quadratic formula;

    x = -b +/- sqrt (-b2 - 4ac)
    for the following questions;

    y = 4x2 - x

    y = 4x2 -1

    y = x2 + 4


    y = -2x2 + 4x

    i ask this as there is no value for (c)

    help me :)
  2. jcsd
  3. Jul 23, 2009 #2


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    Hi JakePearson! :smile:

    (have a square-root: √ and a ± :wink:)

    Yup! You can always use that formula …

    just put c = 0 (or b = 0 as the case may be) :biggrin:
  4. Jul 23, 2009 #3


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    You need to show working before anyone can help you.

    If there is no real root for an answer, usually means the answer is imaginary. As is the case for c)
    Last edited: Jul 23, 2009
  5. Jul 23, 2009 #4
    cheers tiny-tim, thanks, ill use those :)
  6. Jul 23, 2009 #5


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    Gold Member

    Note correction, there's no minus sign in front of the 'b squared' term
    Note that the y value must be zero in order to use the quadratic formula
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