已知x2-x+1=0,求代数式x8+x4+1的值.
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解:∵x2-x+1=0
∴x2=x-1,
∴x8+x4+1=x4(x4+1)+1
=(x2)2[(x2)2+1]+1,
=(x-1)2[(x-1)2+1]+1,
=(x2-2x+1)[(x2-2x+1)+1]+1,
=(x-1-2x+1)(x-1-2x+1+1)+1,
=(-x)(-x+1)+1,
=x2-x+1,
=0.
解析分析:应先根据x2-x+1=0,得到x2=x-1,要求的式子的指数较大,应降次整理.
点评:本题的次数较大,所以基本思路是降次,只要是高于2次的应降次到底.最终得到与所给条件有关的式子.