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Math Help - confused while trying to factor this

  1. #1
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    confused while trying to factor this

    y^3-y^2+3y-3 is what im factoring

    the book says the answer is (y-1)(y^2+3)

    i dont know how it gets there

    heres what i try to do:
    (y^3-y^2)+(3y-3)
    -y^2(y-1) + 3(y-1)

    (y-1)(-y^2+3)

    what am i doing wrong?
    as usual, thanks for any help. this site really helps me out
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  2. #2
    MHF Contributor harish21's Avatar
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    Quote Originally Posted by NecroWinter View Post
    y^3-y^2+3y-3 is what im factoring

    the book says the answer is (y-1)(y^2+3)

    i dont know how it gets there

    heres what i try to do:
    (y^3-y^2)+(3y-3)
    -y^2(y-1) + 3(y-1) : the common factor for the first term should be y^2.

    (y-1)(-y^2+3)

    what am i doing wrong?
    as usual, thanks for any help. this site really helps me out
    Look at the line in red. You error is there.

    (y^3-y^2)+(3y-3)

    =y^2(y-1)+3(y-1) = (y-1)(y^2+3)
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  3. #3
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    ok now that leads me to a new question

    my book has me factoring out negative numbers as well sometimes, how do you know what youre supposed to do? is it just when a negative number is all the way to the left?
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  4. #4
    MHF Contributor harish21's Avatar
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    You can take a negative factor here as well.

    (y^3-y^2)+(3y-3)

    =-y^2(-y+1)-3(-y+1) = (-y+1)(-y^2-3)

    =(-y+1)(-y^2-3)

    =-(y-1)[-(y^2+3)] = (y-1)(y^2+3)

    You can follow whichever way you think is convenient.
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  5. #5
    MHF Contributor harish21's Avatar
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    double posted by mistake..
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