X^3-X^2-X+1=0求解 ？

X^3-X^2-X+1=0
(x^3-x^2)-(x-1)=0
x^2(x-1)-(x-1)=0
(x^2-1)(x-1)=0
(x+1)(x-1)^2=0
x=-1或1

X^3-X^2-X+1=X^2(X-1)-(X-1)=(X^2-1)(X-1)=(X+1)(X-1)(X-1)=(X+1)(X-1)^2=0
所以X+1=0或(X-1)^2=0
所以X=-1或1

X^2(X-1)-(X-1)=(X^2-1）(X-1)=(X+1）（X-1)^2
可知为+1和-1

微分得方程
3x^2-2x-1=0
(3x+1)(x-1)=0
结果就是(-1/3)和1