(x的平方-2x+1)/(x的平方-1)÷(x-1)/(x的平方+x)-x
=(x^2-2x+1)/(x^2-1) * (x^2+x)/(x-1) -x
=(x-1)^2/(x-1)(x+1) *(x+1)x/(x-1) -x
=x-x=0