a) Ta có
$15x^2 y^2 - 6 x^2y -3x^2y^2 = 12x^2y^2 - 6x^2y$
Khi đó
$(12x^2y^2 - 6x^2y): 6x^2y = 2y-1$
b) Ta có
$ (6x^3 - 7x^2 - x + 2) : (2x + 1) = 3x^2 - 5x + 2$
c) Ta có
$(x^4 + x^2 - x^3 + 3x) : (x^2 + 3 - 2x )= (x^4 - x^3 + x^2 + 3x): (x^2-2x+3)$
$= x^2 + x + 3$ dư $9x + 9$