x2(x4 - 1)(x2 + 2) + 1
= x2(x2 - 1)(x2 + 1)(x2 + 2) + 1
= (x4 + x2)(x4 + x2 + 2) + 1
= (x4 + x2)[(x4 + x2) + 2] + 1
= (x4 + x2)2 + 2(x4 + x2).1 + 12
= (x4 + x2 + 1)2
= (x4 - x + x2 + x + 1)2
= [x(x3 - 1) + (x2 + x + 1)]2
= [x(x - 1)(x2 + x + 1) + (x2 + x + 1)]2
= [(x2 + x + 1)(x2 - x + 1)]2
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