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Thread: Solve: 27x^3 - 125 = 0

  1. #1
    New Member
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    Solve: 27x^3 - 125 = 0

    I am reviewing a test that I took. I got part of the answer correct and I am trying to understand how to do the second part correctly.

    Solve: 27x^3 - 125 = 0

    I started by factoring:

    (3x - 5)(9x^2 + 15x + 25) = 0

    3x - 5 = 0

    3x = 5

    x = 5/3

    I am stuck with the second half of the equation as to where to start.

  2. #2
    Senior Member skeeter's Avatar
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    Dec 2005
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    Fort Worth, TX
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    ever used the quadratic formula?

    a = 9, b = 15, c = 25

    fyi, the roots of this quadratic will be imaginary.

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