分解因式x^2-2xy+y^2+2x-2y-8
问题描述：
分解因式x^2-2xy+y^2+2x-2y-8
答
x^2-2xy+y^2+2x-2y-8
=[x^2-2xy+y^2]+2(x-y)-8
=[x-y]^2+2[x-y]-8
=[x-y+4][x-y-2]