Giải thích các bước giải:
a)=(x^2-y^2)-(xy+y)=(x-y)(x+y)-y(x+y)=(x-2y)(x+y)
b)=(x^2-2x+1)-y^2=(x-1)^2-y^2=(x-y-1)(x+y-1)
c)=(x^2+4x+4)-4y^2=(x+2)^2-(2y)^2=(x-2y+2)(x+2y+2)
d)=5(x-y)+a(x-y)=(5+a)(x-y)
e)=z(x-y)-(x^2-2xy+y^2)=z(x-y)-(x-y)^2=(z-x+y)(x-y)