n4+1=n4+2n2+1−2n2=(n2+1)2−2n2=(n2+2−√2n)(n2+2+√2n).
n^4 +1 = (n^4 + 2n^2 +1) -2n^2
=( n^2 +1)^2 -( √2 n)^2
= ( n^2 +1 + √2 n)( n^2 +1- √2 n)
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