1) (9x^4 + 3x^3y) / 2x^3 - (x - 3y)= 9x + 3y - (x - 3y)= 9x + 3y - x + 3y= 8x + 6y
2) (3xy - 12x^2) / 3x + 2(5y + 2x)= y - 4x + 10y + 4x= 11y
3) 2x(3x - y) + (6xy^2 - 18x^2y) / 3y= 6x^2 - 2xy + 2xy - 6x= 6x^2 - 6x
4) (3y - 4x)(7x^2) - (5x^2y^3 + 21x^3y^2) / xy= 21x^2y - 28x^3 - 5xy^2 - 21x^2y= -28x^3 - 5xy^2
1) (9x^4 + 3x^3y) / 2x^3 - (x - 3y)
= 9x + 3y - (x - 3y)
= 9x + 3y - x + 3y
= 8x + 6y
2) (3xy - 12x^2) / 3x + 2(5y + 2x)
= y - 4x + 10y + 4x
= 11y
3) 2x(3x - y) + (6xy^2 - 18x^2y) / 3y
= 6x^2 - 2xy + 2xy - 6x
= 6x^2 - 6x
4) (3y - 4x)(7x^2) - (5x^2y^3 + 21x^3y^2) / xy
= 21x^2y - 28x^3 - 5xy^2 - 21x^2y
= -28x^3 - 5xy^2