初二数学题..帮帮忙..

来源：百度知道 编辑：UC知道 时间：2024/06/15 17:58:31
先简化
[（x^2-2x+1）/(x^2-1)+1/x]÷1/（x+1)

再取一个你认为合理的x值，代入原式求值。

[(x^2-2x+1)/(x^2-1)+1/x]÷1/(x+1)
=[(x-1)^2/(x-1)(x+1)+1/x]÷1/(x+1)
=[(x-1)^2/(x-1)(x+1)+1/x]*(x+1)
=[(x-1)^2/(x-1)(x+1)]*(x+1)+(1/x)*(x+1)
=[(x-1)^2/(x-1)]+[(x+1)/x]
=(x-1)+[(x+1)/x]
=[x(x-1)+(x+1)]/x
=(x^2+1)/x
将x=1代入得:
(1+1)/1=2

原式=[(x-1)^2/(x+1)(x-1)+1/x]*(x+1)=[(x-1)/(x+1)+1/x]*(x+1)=(x-1)+(x+1)/x=x-1+1+1/x=x+1/x
取x=2(只要x不等于0即可),则原式=2.5