Đáp án:
`1, x^2+x-6=x^2-2x+3x-6=x(x-2)+3(x-2)=(x-2)(x+3)`
`2, x^2y-xy^2+x^3-y^3=xy(x-y)+(x-y)(x^2+xy+y^2)=(x-y)(xy+x^2+xy+y^2)=(x-y)(x+y)^2`
`4, x^2y^2-4x^2-y^2+4=(x^2y^2-y^2)-(4x^2-4)`
`=y^2(x^2-1)-4(x^2-1)`
`=(x^2-1)(y^2-4)`
`=(x-1)(x+1)(y-2)(y+2)`
`5, x^3-3x^2+3x-1-y^3=(x-1)^3-y^3`
`=(x-1-y)[(x-1)^2+(x-1)y+y^2]`
`=(x-y-1)(x^2-2x+1+xy-y+y^2)`
`6, x^6-y^6=(x^3-y^3)(x^3+y^3)`
`=(x-y)(x^2+xy+y^2)(x+y)(x^2-xy+y^2)`
`7, 2x^2+2y^2-x^2.z +z-y^2.z-2`
`=(2x^2+2y^2-2)-(x^2.z+y^2.z-z)`
`=2(x^2+y^2-1)-z(x^2+y^2-1)`
`=(x^2+y^2-1)(2-z)`