Sorry I failed to make Latex work, don't know why... 1. The problem statement, all variables and given/known data We consider for a given potential. Psi is also normalized... 2. Relevant equations Show that expectation value of energy is independent of time. 3. The attempt at a solution Well, I'm use to expecting values, but not of the energy... I started with <H>psi=<E>psi then if I compute <H>=<psi|H|psi> = E|Psi> = E Then I told myself H=p^2/2m + V(x) So I guess if I compute dH/dt and I find it equals to 0 I can say E is independent of time? I feel like this is wrong tough... It looks too simple Thanks a lot for checking that out guys!