
I thought my solution was correct - but it seems like that's not the case. Can anyone possibly explain to me why I'm wrong?

I thought my solution was correct - but it seems like that's not the case. Can anyone possibly explain to me why I'm wrong?
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It's clear that $x^2 + 1$ is an irreducible quadratic. On the other hand, using the fact that $x^2 - 1 = (x - 1)(x + 1)$, we can rewrite the expression as
$$(x - 1)^2 (x + 1)^2 (x^2 + 1)^2$$
How many linear terms are there now?