先化簡,再求值:1x+1−1x2−1÷x+1x2−2x+1,其中x=3-1.

先化簡,再求值:1x+1−1x2−1÷x+1x2−2x+1,其中x=3-1.

原式=1x+1−1(x+1)(x−1)•(x−1)2x+1=1x+1−x−1(x+1)2=(x+1)−(x−1)(x+1)2=2(x+1)2,當x=3-1時,原式=2(3−1+1)2=23.