Let’s check degree: the leading term of \( f(x) \) is \( x \), so \( f(f(x)) \) has leading term \( f(x) o x \), so \( f(f(x)) o x \), but as a rational function, \( f(f(x)) = x + o(1) \), but algebraically, the numerator leads to degree 9. - go-checkin.com