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Math Help - Rearranging negative polynomials

  1. #1
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    Rearranging negative polynomials

    Given 6 + 2x + 3x3 - x4, how would I rearrange it into descending order to be factored? I know addition is commutative, but given that x4 is negative, how do I move that without changing the expression?
    Last edited by zsf1990; January 18th 2013 at 10:05 PM.
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  2. #2
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    Re: Rearranging negative polynomials

    Hey zsf1990.

    Try using:

    6 + 2x + 3x^3 - x^4 = - (x^4 - 3x^3 - 2x - 6)
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    Re: Rearranging negative polynomials

    Thanks! Any chance you could explain how to factor 5x3 - 40? -40 isn't a perfect cube, so I'm feeling lost. This is what I get for missing a lecture I guess.

    EDIT: Nevermind. Factor out a five to get x3 - 8, which is a difference of cubes. It's always the little things, lol.
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    Re: Rearranging negative polynomials

    Quote Originally Posted by zsf1990 View Post
    Thanks! Any chance you could explain how to factor 5x3 - 40? -40 isn't a perfect cube, so I'm feeling lost. This is what I get for missing a lecture I guess.

    EDIT: Nevermind. Factor out a five to get x3 - 8, which is a difference of cubes. It's always the little things, lol.
    You have a typo in the question,
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    Re: Rearranging negative polynomials

    I'm not sure I'm following. The question mark is a typo?
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    Re: Rearranging negative polynomials

    Quote Originally Posted by Plato View Post
    You have a typo in the question,
    Did you want to factor 5x^3-40~?

    You seemed to say factor 5x^3-40?-40
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  7. #7
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    Re: Rearranging negative polynomials

    Ah. My bad. It was factor 5x[sup]3 - 40.

    As I move on with my homework, what are the steps to factoring this polynomial? 5(3-4x)2 - 8(3-4x) (5x-1) I'm not sure where to start.
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  8. #8
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    Re: Rearranging negative polynomials

    Quote Originally Posted by Plato View Post
    Did you want to factor 5x^3-40~?

    You seemed to say factor 5x^3-40?-40
    No, the OP asked how to factor \displaystyle \begin{align*} 5x^3 - 40 \end{align*} and then went on to say in the next sentence that -40 is not a perfect cube.
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