分解因式3x的四次方-9x的三次方-27x²-81x =3x(x^3-3x^2-9x-27)=3x(x^2(x-3)-9(x+3)) 分解因式x²-x²y+xy²-x+y-y²=x²(1-y)+x(y²-1)+y(1-y)=(x²+y)(1-y)+x(y-1)(y+1)=(x²...