若x=根号2-1,求代数式x的三次方+x的二次方-x-1的值
1个回答
2014-03-26
展开全部
x^3+x^2-x-1
=x^2(x+1)-(x+1)
=(x+1)(x^2-1)
=(x+1)(x+1)(x-1)
=(x+1)^2(x-1)
=2*(根号2-2)
=x^2(x+1)-(x+1)
=(x+1)(x^2-1)
=(x+1)(x+1)(x-1)
=(x+1)^2(x-1)
=2*(根号2-2)
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