1) (a+2b)(a^2-2ab+3b^3) = a(a^2-2ab+3b^3) + 2b(a^2-2ab+3b^3)= a^3 - 2a^2b + 3ab^3 + 2a^2b - 4ab^2 + 6b^4= a^3 - a^2b + 3ab^3 - 4ab^2 + 6b^4
2) (2x^2-3xy-4y^2)(3x-4y) = 2x^2(3x-4y) - 3xy(3x-4y) - 4y^2(3x-4y)= 6x^3 - 8x^2y - 9x^2y + 12xy^2 - 12x^2y + 16xy^2 + 12y^3 - 16y^2= 6x^3 - 17x^2y + 28xy^2 - 16y^2
1) (a+2b)(a^2-2ab+3b^3) = a(a^2-2ab+3b^3) + 2b(a^2-2ab+3b^3)
= a^3 - 2a^2b + 3ab^3 + 2a^2b - 4ab^2 + 6b^4
= a^3 - a^2b + 3ab^3 - 4ab^2 + 6b^4
2) (2x^2-3xy-4y^2)(3x-4y) = 2x^2(3x-4y) - 3xy(3x-4y) - 4y^2(3x-4y)
= 6x^3 - 8x^2y - 9x^2y + 12xy^2 - 12x^2y + 16xy^2 + 12y^3 - 16y^2
= 6x^3 - 17x^2y + 28xy^2 - 16y^2