Преобразуйте в многочлен выражение (a+b)(c-d)

1) $$(a+b)(c-d) = ac - ad + bc - bd$$ 2) $$(x-6)(x-4) = x^2 - 4x - 6x + 24 = x^2 - 10x + 24$$ 3) $$(a-3)(a+7) = a^2 + 7a - 3a - 21 = a^2 + 4a - 21$$ 4) $$(11-c)(c+8) = 11c + 88 - c^2 - 8c = -c^2 + 3c + 88$$ 5) $$(d+13)(2d-1) = 2d^2 - d + 26d - 13 = 2d^2 + 25d - 13$$ 6) $$(3y-5)(2y-12) = 6y^2 - 36y - 10y + 60 = 6y^2 - 46y + 60$$ 7) $$(2x^2-3)(x^2+4) = 2x^4 + 8x^2 - 3x^2 - 12 = 2x^4 + 5x^2 - 12$$ 8) $$(x-6)(x^2-2x+9) = x^3 - 2x^2 + 9x - 6x^2 + 12x - 54 = x^3 - 8x^2 + 21x - 54$$ 9) $$(5x-y)(2x^2+xy-3y^2) = 10x^3 + 5x^2y - 15xy^2 - 2x^2y - xy^2 + 3y^3 = 10x^3 + 3x^2y - 16xy^2 + 3y^3$$ 10) $$b(6b+7)(3b-4) = b(18b^2 - 24b + 21b - 28) = b(18b^2 - 3b - 28) = 18b^3 - 3b^2 - 28b$$