Bài 1: a, 2x^2-2xy-3x+3y=(2x^2-2xy)-(3x-3y)=2x(x-y)-3(x-y)=(2x-3)(x-y)
b, x^4-9x^3+x^2-9x=(x^4-9x^3)+(x^2-9x)=x^3(x-9)+x(x-9)=(x^3+x)(x-9)=x(x^2+1)(x-9)
c, x^2-4x^2y^2+y^2+2xy=(x^2+2xy+y^2)-4x^2y^2=(x+y)^2-4x^2y^2=(x+y-2xy)(x+y+2xy)
d, x^2(x-3)^2-(x-3)^2-x^2+1=(x-3)^2(x^2-1)-(x^2-1)=(x^2-1)[(x-3)^2-1]=(x-1)(x+1)(x-4)(x-2)