Bài 1
a) Ta có
$(2x^2y + 3xy - 3xy)xy = (2x^2y + 0) xy$
$= 2x^2y . xy$
$=2x^3 y^2$
b) Ta có
$(x - 4x + 4):(x-2) = (4-3x) : (x-2) = (4-2x - x) : (x-2)$
$= (4-2x) : (x-2) - \dfrac{x}{x-2}$
$= -2 - \dfrac{x}{x-2}$
Bài 2
a) $xy -3x = x(y-3)$
b) $x^2 - xy + x-y = x(x-y) + 1(x-y) = (x+1)(x-y)$