x⁴ + 4x² + 3 +1 - 1 = ( x² )² + 4x² + 4 - 1 = ( x² + 2 )² - 1 =
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= ( x² + 2 -1) · ( x² + 2 + 1 ) = ( x² + 1) · ( x² + 3)
x⁴ + 2x² + 1 - 3 - 1 = ( x² )² + 2x² + 1 - 4 = ( x² + 1) ² - 4 =
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= ( x² + 1) ² - 2² = ( x² + 1 -2) · ( x² + 1 + 2) = ( x² - 1) · ( x² + 3)
ex = ( x² + 1) · ( x² + 3) / ( x² - 1 ) ·( x² + 3 ) se simplifica cu x² + 3
F(x) = ( x² + 1 ) / ( x² - 1 )