# factoring polynomial equations

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• Oct 29th 2012, 04:44 PM
maria1234567
factoring polynomial equations
81x^4-256

im working on a problem and need to factor the above equation. thanks for your help in advance.
• Oct 29th 2012, 04:54 PM
Prove It
Re: factoring polynomial equations
\displaystyle \begin{align*} 81x^4 - 256 &= \left( 9x^2 \right)^2 - 16^2 \\ &= \left( 9x^2 - 16 \right) \left( 9x^2 + 16 \right) \\ &= \left[ \left(3x \right)^2 - 4^2 \right] \left( 9x^2 + 16 \right) \\ &= \left( 3x - 4 \right) \left( 3x + 4 \right) \left( 9x^2 + 16 \right) \end{align*}