y=（2x-1)/(x+1)
xy+y=2x-1
2x-xy=y+1
x(2-y)=y+1
x=(y+1)/(2-y)
即
f(x)=（2x-1)/(x+1)的反函数是 f(x)=(x+1)/(2-x)
定义域是 x∈R且x≠2