SOLUTION: Factor x^4

SOLUTION: Factor x^4 - 81

Question 754133: Factor
x^4 - 81
Answer by nerdybill(7384) (Show Source): You can put this solution on YOUR website!
x^4 - 81
can be rewritten as:
(x^2)^2 - (9)^2
this is a "difference of squares" (special case factors to):
(x^2 - 9)(x^2 + 9)
But, the left term can be rewritten as:
(x^2 - 3^2)(x^2 + 9)
another "difference of squares":
(x-3)(x+3)(x^2+9) (final factored form)
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