1) $$2y(y^5 - 3y^3 + 8) = 2y^6 - 6y^4 + 16y$$
2) $$(x-4)(3x-5) = 3x^2 - 5x - 12x + 20 = 3x^2 - 17x + 20$$
3) $$(8x-7y)(2x+5y) = 16x^2 + 40xy - 14xy - 35y^2 = 16x^2 + 26xy - 35y^2$$
4) $$(x-2)(x^2-x-3) = x^3 - x^2 - 3x - 2x^2 + 2x + 6 = x^3 - 3x^2 - x + 6$$