课堂上,李老师给大家出了一道题：当x=3,1/2,6/7时,求代数式x^2-2x+1/x^2-1÷2x-2/x+1的值

由（x²-2x+1）/（x²-1）÷(2x-2)/(x+1)
=(x-1)²/(x+1)(x-1)÷2(x-1)/(x+1)
=(x-1)²/(x+1)(x-1)×(x+1)2(x-1)
=1/2是恒等式,
∴当x=3,/2,6/7时,
（x²-2x+1）/（x²-1）÷(2x-2)/(x+1)=1/2.