Упростите выражение:
1) (x + 1)(x − 1) − (x + 5)(x − 5) + (x + 1)(x − 5);
2) $81a^8 - (3a^2 - b^3)(9a^4 + b^6)(3a^2 + b^3)$.
$(x + 1)(x - 1) - (x + 5)(x - 5) + (x + 1)(x - 5) = x^2 - 1 - (x^2 - 25) + (x^2 + x - 5x - 5) = x^2 - 1 - x^2 + 25 + x^2 + x - 5x - 5 = (x^2 - x^2 + x^2) + (x - 5x) + (-1 + 25 - 5) = x^2 - 4x + 19$
$81a^8 - (3a^2 - b^3)(9a^4 + b^6)(3a^2 + b^3) = 81a^8 - (9a^4 - b^6)(9a^4 + b^6) = 81a^8 - (81a^8 - b^{12}) = 81a^8 - 81a^8 + b^{12} = b^{12}$
Пожауйста, оцените решение
