How to solve the equation $(f \circ f)(x)=x$? Solve the equation $(f \circ f)(x)=x$, if $f(x) = \frac {2x+1}{x+2}$ and $x \in \mathbb R$ \ $\{-2\}$.
How would I solve this equation and what does it even mean to be solved in this context?

How to begin:
$$f\bigl(f(x)\bigr)=\frac{2f(x)+1}{f(x)+2}=\frac{2\cfrac{2x+1}{x+2}+1}{\cfrac{2x+1}{x+2}+2}=\cdots$$
