题目
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
提问时间：2020-06-13
答案
由题意知
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
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
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