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Thread: Factoring Help - hw due help!

  1. #1
    dahcetmoht
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    Factoring Help - hw due help!

    Math HW due.. need help tonight bad.

    Need to factor the following
    (If I erase some of the problems, its because someone already did them. thanks)

    2. 27x^3-64

    3. 3x^3+x^2-12x-4
    Last edited by dahcetmoht; Mar 3rd 2008 at 07:57 PM.
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  2. #2
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    $\displaystyle 27x^3 - 64$ is a difference of two cubes - consider it written as $\displaystyle (3x)^3 - 4^3$. Use the formula for difference of two cubes with $\displaystyle a=3x$ and $\displaystyle b=4$.

    For the other problem, $\displaystyle 3x^3+x^2-12x-4$, out of the first two terms, factor $\displaystyle x^2$ and out of the last two terms factor out -4. This gives:

    $\displaystyle x^2(3x+1)-4(3x+1)$. Now, both terms have a $\displaystyle (3x+1)$ in common, so factor that out, giving:

    $\displaystyle (3x+1)(x^2-4)$. The last step for finishing this one is to factpr $\displaystyle x^2-4$, which is a difference of squares.

    Hope this helps!
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