x2-5x-1=0,求x4+1/x4的值
问题描述:
x2-5x-1=0,求x4+1/x4的值
x2-5x-1=0两边同时除以X
x-5-1/x=0
x-1/x=5两边平方
x2-2+1/x2=25
x2+1/x2=27在两边平方
x4+2+1/x4=729
x4+1/x4=727
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答
x2-5x-1=0
显然x≠0
x-5-1/x=0
x-1/x=5
平方
x2+1/x2-2=25
x2+1/x2=27
平方
x4+1/x4+2=729
x4+1/x4=727
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