a/ $xz+yz-5x-5y\\=(xz+yz)-(5x+5y)\\=z(x+y)-5(x+y)\\=(z-5)(x+y)$
Vậy $xz+yz-5x-5y=(z-5)(x+y)$
b/ $x^2-2xy+y^2-z^2\\=(x^2-2xy+y^2)-z^2\\=(x-y)^2-z^2\\=[(x-y)-z][(x-y)+z]\\=(x-y-z)(x-y+z)$
Vậy $x^2-2xy+y^2-z^2=(x-y-z)(x-y+z)$
c/ $x^3+2x^2y+xy^2-9x\\=x(x^2+2xy+y^2-9)\\=x[(x^2+2xy+y^2)-3^2]\\=x[(x+y)^2-3^2]\\=x(x+y-3)(x+y+3)$
Vậy $x^3+2x^2y+xy^2-9x=x(x+y-3)(x+y+3)$
d/ $x^2-y^2-5x+5y\\=(x^2-y^2)-(5x-5y)\\=(x-y)(x+y)-5(x-y)\\=(x-y)(x+y-5)$
Vậy $x^2-y^2-5x+5y=(x-y)(x+y-5)$
e/ $5x^3+5x^2y-10x^2-10xy\\=5x(x^2+xy-2x-2y)\\=5x[(x^2+xy)-(2x+2y)]\\=5x[x(x+y)-2(x+y)]\\=5x(x-2)(x+y)$
Vậy $5x^3+5x^2y-10x^2-10xy=5x(x-2)(x+y)$
f/ $x^2-6x+8\\=x^2-4x-2x+8\\=(x^2-4x)-(2x-8)\\=x(x-4)-2(x-4)\\=(x-2)(x-4)$
Vậy $x^2-6x+8=(x-2)(x-4)$
