# Why isn’t factoring x^4 - 81 as (x^2 + 9)(x^2 - 9) a complete factorization?

Why isn’t factoring ${x}^{4}-81as\left({x}^{2}+9\right)\left({x}^{2}-9\right)$ a complete factorization?
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Step 1
Given statement is
is complete factorization.
Step 2
$\because \left({x}^{2}-9\right)$ factors are also possible.
$\therefore \left({x}^{2}+9\right)\left({x}^{2}-9\right)$ is not complete factorization of ${x}^{4}-81$.
Step 3
are
$\left({x}^{2}-9\right)=\left(x+3\right)\left(x-3\right)$
.