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Prove please

  1. Oct 25, 2006 #1
    Prove that the sum of the roots and product of the roots of the equation
    ax^2 + bx + c = 0 are
    -b/a and c/a respectively
    thank you
     
  2. jcsd
  3. Oct 25, 2006 #2
    Do you know what the quadratic formula is?
     
  4. Oct 26, 2006 #3

    matt grime

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    You don't need that. You dont' need to know what the roots are at all. You can let them be r and s, and just use standard results such as if r is a root of f(x), then f(x) = (x-r)g(x) for some g(x). I.e. just factorize the equation.
     
  5. Oct 26, 2006 #4

    HallsofIvy

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    Staff Emeritus
    Science Advisor

    If u and v are roots of that equation then
    [tex]ax^2+ bx+ c= a(x- u)(x- v)[/itex]
    Multiply the right side and compare corresponding coefficients.
     
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