^3代表3次方,^2代表平方
X^3 + X^2 - Y^3 - Y^2
=(x^3 - y^3) + (x^2 - y^2)
=(x-y)(x^2+xy+y^2) + (x-y)(x+y)
=(x-y)(x^2 + xy + y^2 + x + y)
应该不能再往下化了吧