Rút gọn

Rút gọn:
5. (2x+y)³ + (y-x)³
6. 2(y-x)³ - (2x-y)³
7. (2x+y)³ - (x-2y)³
8. (2x-3)³ - 2x(2x+1)²
9. (3x-1)³ - 27x²(x-1)
10. (2x+1)³ - 8x(x-1)²
11. (x+1)³ - (x-4)(x+4) + x³
12. (x+2)³ - x(x+3)(x-3)
13. (x-2)³ - x(x-2)(x+2) + 6x(x-3)
14. x(x-5)(x+5) - (x-5) + 100x