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已知x的平方+x-1=0,求x[(1-2/1-x)/(x+1)-x的平方-1/x的平方-2x+1]的值
人气:142 ℃ 时间:2020-05-24 09:53:15
解答
x{[1-2/(1-x)]/(x+1)-(x^2-1)/(x^2-2x+1)}
=x{[-(x+1)/(1-x)]/(x+1)-(x-1)(x+1)/(x-1)^2}
=x{-1/(1-x)-(x+1)/(x-1)}
=-x^2/(x-1),
因为x^2+x-1=0,
所以x^2=-(x-1),
所以原式=1.
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