No reason to stop there. Factor out all those 3's:
81(x^2+1)(x-1)(x+1)
If you must pick one of those choices, then use the last one, since it factors the 9x^2-9 as well. (factor completely!)
factor completely
81x^4 - 81
possible choices are::
(9x^2 + 9)(9x^2 - 9)
OR
(9x^2 +9)(3x + 3)(3x - 3)
2 answers
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