6x^3y^2-4x^2y^3+2x^2y^2
=2x^2y^2(3x-2y+1)
144x^2-256y^2
=(12x+16y)(12x-16y)
=16(3x+4y)(3x-4y)
25*(x-1)^2-10(x-1)+1
={5(x-1)-1}^2
=(5x-6)^2
（2x-y)^2-(x-y)^2
=(2x-y+x-y)(2x-y-x+y)
=3x(3x-2y)