（2014•孟津县二模）先化简，再求值：（x2−1x2−2x+1+1−xx+1）÷xx−1，并从-1≤x≤3中选一个合适的整数x代入求值．

Question

（2014•孟津县二模）先化简，再求值：（(x2−1)/(x2−2x+1)+(1−x)/(x+1)）÷(x)/(x−1)，并从-1≤x≤3中选一个合适的整数x代入求值．

Answer 1

原式=[((x+1)(x−1))/((x−1)2)-(x−1)/(x+1)]•(x−1)/(x)
=（(x+1)/(x−1)-(x−1)/(x+1)）•(x−1)/(x)
=((x+1)2−(x−1)2)/((x+1)(x−1))•(x−1)/(x)
=(4x)/((x+1)(x−1))•(x−1)/(x)
=(4)/(x+1)，
当x=3时，原式=(4)/(3+1)=1．