Express x⁴ + y⁴ + z⁴ - 2y²z² - 2z²x² - 2x²y² as the product of four factors.

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Homework Statement



Express x^4 + y^4 + z^4 - 2y^2z^2 - 2z^2x^2 - 2x^2y^2 as the product of four factors.


2. The attempt at a solution

(x-y-z)(-x+y-z)(-x-y+z)(x+y+z)
 
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If you really just want someone to check, that works fine.
 
Ok, thanks!
 
Since ##px^9+q## is the factor, then ##x^9=\frac{-q}{p}## will be one of the roots. Let ##f(x)=27x^{18}+bx^9+70##, then: $$27\left(\frac{-q}{p}\right)^2+b\left(\frac{-q}{p}\right)+70=0$$ $$b=27 \frac{q}{p}+70 \frac{p}{q}$$ $$b=\frac{27q^2+70p^2}{pq}$$ From this expression, it looks like there is no greatest value of ##b## because increasing the value of ##p## and ##q## will also increase the value of ##b##. How to find the greatest value of ##b##? Thanks
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