(а⁻²+1)(а⁻²-1)-(а⁻²+1)²+2= ((1/а)² + 1 )((1/а)² - 1 )-((1/а)² + 1 )²+2 =
= ((1/а)⁴ - 1 )- ( (1/а)⁴ +(2/а²) +1 ) +2= (1/а)⁴ - 1 - (1/а)⁴ -(2/а²) -1 +2 = - (2/а²)
(а⁻²+1)(а⁻²-1)-(а⁻²+1)²+2= ((1/а)² + 1 )((1/а)² - 1 )-((1/а)² + 1 )²+2 =
= ((1/а)⁴ - 1 )- ( (1/а)⁴ +(2/а²) +1 ) +2= (1/а)⁴ - 1 - (1/а)⁴ -(2/а²) -1 +2 = - (2/а²)