令y=f(x)=(x+1)/(x-1)，那么：y(x-1)=x+1yx-y=x+1x(y-1)=y+1x=(y+1)/(y-1) （y≠1）那么：f^-1（x）=(x+1)/(x-1)所以：f^-1（1/x）=(1/x+1)/(1/x-1)=(1+x)/(1-x)
