Question

先化简,再求值:(X-1/X平方-1)-(X/X+1),其中X=2

Answer 1

您好：

(X-1/X平方-1)-(X/X+1)
=（x-1）/(x+1)(x-1)-x/(x+1)
=1/(x+1)-x/(x+1)
=(1-x)/(x+1)
=(1-2)/(2+1)
=-1/3

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追问

答案书化简后是X

Answer 2

解：
(x-1)/(x²-1)-x/(x+1)
=(x-1)/[(x+1)(x-1)]-x/(x+1)
=1/(x+1)-x/(x+1)
=(1-x)/(x+1)
=(1-2)/(2+1)
=-1/3