已知x的2次方减x减1等于 0，试求x的3次方减2x减1的值

---

x^3-2x-1
=(x^3-x)-(x+1)
=x(x^2-1)-(x+1)
=x(x+1)(x-1)-(x+1)
=(x+1)(x^2-x-1)
而由题目得：x^2-x-1=0
所以指兄携上式唯伏值尘备为0

---

由乎绝题和槐意知唤顷友
x^2-x-1=0
即x^2-1=x x+1=x^2
x^3-2x-1
=x(x^2-1)-(x+1)
=x^2-x^2
=0

---