+128407 (3x^2-4y)(2x^3+5y)
Distribute the first term in the first set of parentheses over the two terms in the second set
3x^2 * 2x^3 + 3x^2 *5y = 6x^5 + 15x^2y (1)
Distribute the second term in the first set of parenthesesover the two terms in the second set
-4y*2x^3 - 4y*5y = -8yx^3 - 20y^2 (2)
Combine (1) and (2)
6x^5 + 15x^2y - 8x^3y - 20y^2
