Which of these functions is its own inverse?
f(x)=1/xf(x) = 1/xf(x)=1/x
f(x)=x+1f(x) = x+1f(x)=x+1
f(x)=2xf(x) = 2xf(x)=2x
f(x)=x2f(x) = x^2f(x)=x2