1. The problem statement, all variables and given/known data Is the commutator of x and any function of x zero? 2. Relevant equations Taylor's theorem allows such a function to be expanded into polynomials, so that [f(x),x] may be expanded into terms of [x^n,x], which are all zero. Hence, f(x) and x commute. 3. The attempt at a solution Is this a valid demonstration?