Выражение(x+1)(x-+5)(x-5)+(x+1)(x-5) и 81a^8-(3a^2-b^3)(9a^4+b^6)(3a^2+b^3)

   (a-b)(a+b) = a² - b²

1)

(x+1)(x-1)-(x+5)(x-5)+(x+1)(x-5) =

= (x²-1) - (x² - 5²) + (x+1)(x-5) =

= x²-1-x²+25 + (x+1)(x-5) =

= 24 + x²+x-5x-5 = 

= x² - 4x + 19

2)

81a⁸-(3a²-b³)(9a⁴+b⁶)(3a²+b³) = 

= 81a⁸-(3a²-b³)(3a²+b³) (9a⁴+b⁶) =

= 81a⁸- ((3a²)²-(b³)²) (9a⁴+b⁶) =

=  81a⁸- (9a⁴-b⁶) (9a⁴+b⁶) = 

=  81a⁸- ((9a⁴)² - (b⁶)²) =

=  81a⁸- 81a⁸ + b¹² = b¹²