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Math Help - How to find the zeros of an equation?

  1. #1
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    How to find the zeros of an equation?

    How would I find these zeros? I tried factoring by grouping but it doesnt give me the correct answer:

    y=-4x^3+12x^2+96x+112

    The first term is negative
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  2. #2
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    Quote Originally Posted by nascar77 View Post
    How would I find these zeros? I tried factoring by grouping but it doesnt give me the correct answer:

    y=-4x^3+12x^2+96x+112

    The first term is negative
    y = -4(x^3 - 3x^2 - 24x - 28)

    using the rational root theorem, x = -2 is a zero for (x^3 - 3x^2 - 24x - 28) ... you should be able to find the two other zeros with that piece of information.
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    #1 - Simplify your life. Same solutions as this: 0 = x^3 - 3x^2 - 24x - 28

    #2 - Rule of Signs: One Positive Real. Two or Zero Negative

    #3 - Rational Roots: +/-1, +/-2, +/-4, +/-7, +/-14, +/-28
    --------- 7 Works

    #4 - Reduction: (x^3 - 3x^2 - 24x - 28)/(x - 7) = (x^2 + 4x + 4)

    #5 - That is easily factored.
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