Which of the following functions is an involution on the domain R∖{2}\mathbb{R} \setminus \{2\}R∖{2}?
f(x)=2xx−2f(x) = \frac{2x}{x-2}f(x)=x−22x
f(x)=2x+1x−2f(x) = \frac{2x+1}{x-2}f(x)=x−22x+1
f(x)=x+2x−1f(x) = \frac{x+2}{x-1}f(x)=x−1x+2
f(x)=x2x−1f(x) = \frac{x}{2x-1}f(x)=2x−1x