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Math Help - can someone please factor this???

  1. #1
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    can someone please factor this???

    can someone please factor this for me?? if it cant be factored can you explain why? thanks

    (x-y)(x^2-z^2)-(x-z)(x^2-y^2)
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  2. #2
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    Quote Originally Posted by bcguy87 View Post
    can someone please factor this for me?? if it cant be factored can you explain why? thanks

    (x-y)(x^2-z^2)-(x-z)(x^2-y^2)
    You are supposed to know that

    a^2-b^2=(a+b)(a-b)

    Therefore you get:

    (x-y)(x^2-z^2)-(x-z)(x^2-y^2) = (x-y) \left((x+z)(x-z)  \right) - (x-z)\left((x+y)(x-y)  \right)

    You see that the common factor is (x-y)(x-z). Factor out:

    (x-y) \left((x+z)(x-z)  \right) - (x-z)\left((x+y)(x-y)  \right) = (x-y)(x-z) \left((x+z) - (x+y)  \right) = (x-y)(x-z)(z-y)
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  3. #3
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    ok, so how come when u work backwards now from what you got, the answer is not anywhere near what the question was??
    because, when u reverse your factoring method, you are supposed to get the original question................


    i took your a^2-b^2 then i worked it out to get a^2-ab+ab-b^2 then when worked back i got your original question..............just a thought
    Last edited by mr fantastic; March 3rd 2009 at 11:43 PM. Reason: Merged posts
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  4. #4
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    Quote Originally Posted by bcguy87 View Post
    ok, so how come when u work backwards now from what you got, the answer is not anywhere near what the question was??
    ...
    Take your original term and expand the brackets:

    (x-y)(x^2-z^2)-(x-z)(x^2-y^2) = x^2z - x^2y - xz^2 + xy^2 + yz^2 - y^2z

    Now take my result and expand the brackets:

    <br />
 (x-y)(x-z)(z-y) = - x^2y + x^2z + xy^2 - xz^2 - y^2z + yz^2<br />

    If you compare both results you'll see that they are equal.
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