(x+1/x-1+1/x^2-2x+1)除以x/x+1
=[(x+1)/(x-1)+1/(x-1)²]÷x/(x+1)
=(x²-1+1)/(x-1)²÷x/(x-1)
=x/(x-1) 设 x=0
=0/(0-1)
=0