令f(x)=y,则y=x/(x-2)
y(x-2)=x
xy-x=2y
x(y-1)=2y
x=2y/(y-1)
f-1(x)=2x/(x-1)
f-1(2x)=4x/(2x-1)=2x
∴(4x-2x(2x-1))(2x-1)=0
=> 2x-1=0或2-(2x-1)=0
=> x=1/2或 2x=3
=> x=1/2或x=3/2