1) (d-5)(9d+1)(3d-9) = (9d²+d-45d-5)(3d-9) = (9d²-44d-5)(3d-9) = 27d³-81d²-132d²+396d-15d+45 = 27d³-213d²+381d+45
2) (b³+4b+2)(-b³-4b+2) = (2+b³+4b)(2-b³-4b) = 4-(b³+4b)² = 4-(b⁶+8b⁴+16b²) = 4-b⁶-8b⁴-16b² = -b⁶-8b⁴-16b²+4
3) (x+y)(x²-3x²y+2xy²+y²) = x³-3x³y+2x²y²+xy²+x²y-3x²y²+2x³+y³ = x³-3x³y-x²y²+xy²+x²y+2xy³+y³