閱讀并按要求完成各題．
（1）在化簡數(shù)學公式的過程中，小王和小李的化簡結果不一樣：
小王的化簡過程如下：
原式=數(shù)學公式=數(shù)學公式=數(shù)學公式．
小李的化簡過程如下：
原式=數(shù)學公式=數(shù)學公式=數(shù)學公式．
請判斷誰的化簡結果正確，并說明理由．
（2）已知數(shù)學公式，求數(shù)學公式數(shù)學公式的值．（結果保留根號）

解：（1）小李的化簡結果正確．理由如下：
=|-|=-；
（2）x====-1，
原式=•
=，
當x=-1時，原式==3+．
分析：（1）根據(jù)二次根式的性質得到=|-|=-，由此可判斷小李的化簡結果正確．
（2）理由（1）的方法可化簡x得到x=-1，再對分式進行通分、約分得到原式=，然后把x的值代入后解分母有理化即可．
點評：本題考查了二次根式的化簡求值：先化簡再代入求值；二次根式運算的最后，注意結果要化到最簡二次根式，二次根式的乘除運算要與加減運算區(qū)分，避免互相干擾．也考查了分式的化簡求值．
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