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Math Help - Is this correct?

  1. #1
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    Is this correct?

    I was assigned homework for the long weekend. I was asked to answer the following question:

    Factor Completely: (2x^4-11x^3+12x^2+x-4)

    I got (x-1) as a factor. Then I divided (2x^4-11x^3+12x^2+x-4) by (x-1) to get (2x^3-9x^2+x+4).

    After I got that answer, I used (x-1) as a factor, which it worked. So I divided (2x^3-9x^2+x+4) by (x-1). To get (2x^2+11x+14)+18/(x-1).

    After that I decomposed (2x^3-9x^2+x+4) to get (x+2)(2x+7).

    After that I put my therefore stated as (x-1)(x+2)(2x+7)+18/(x-1) = (2x^4-11x^3+12x^2+x-4). Therefore the zeros are:  x = 1, -2, -7/2

    Am I correct?
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  2. #2
    MHF Contributor Amer's Avatar
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    Quote Originally Posted by Barthayn View Post
    I was assigned homework for the long weekend. I was asked to answer the following question:

    Factor Completely: (2x^4-11x^3+12x^2+x-4)

    I got (x-1) as a factor. Then I divided (2x^4-11x^3+12x^2+x-4) by (x-1) to get (2x^3-9x^2+x+4).

    After I got that answer, I used (x-1) as a factor, which it worked. So I divided (2x^3-9x^2+x+4) by (x-1). To get (2x^2+11x+14)+18/(x-1).

    After that I decomposed (2x^3-9x^2+x+4) to get (x+2)(2x+7).

    After that I put my therefore stated as (x-1)(x+2)(2x+7)+18/(x-1) = (2x^4-11x^3+12x^2+x-4). Therefore the zeros are:  x = 1, -2, -7/2

    Am I correct?
    2x^4-11x^3+12x^2+x-4 = (x-1)(x-1)(2x^2-7x-4)

    since 2x^4-11x^3+12x^2+x-4 = (x-1)(2x^3-9x^2+3x+4)

    and 2x^3-9x^2+3x+4=(x-1)(2x^2-7x-4) and

    2x^2-7x-4 = (2x+1)(x-4)
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  3. #3
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    I do not understand where I went wrong. Can you explain more for me in words instead of mathematical equations?

    EDIT: Never mind, I seen where I went wrong. Thank you for your help
    Last edited by Barthayn; October 1st 2009 at 06:43 PM. Reason: Got correct answer.
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