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x²(x⁴ -1) (x² + 2) + 1

= x² ( x² -1)(x²+1)(x² + 2) +1 

= ( x⁴ + x²) (x⁴ + x² - 2) +1

= (x⁴ + x²)² - 2( x⁴ + x²) +1  = (x⁴ + x² - 1)²