Let A and B be two arbitrary observables. Is their commutator Hermitian? Unitary? Anything else? Justify your answer with a rigorous derivation.
Prove the following relations where A and B are two arbitrary operators and a, b ∈ C:
[aA, bB] = ab[A, B]
[A + B, C] = [A, C] + [B, C]
[A, B + C] = [A, B] + [A, C]
[A, BC] = B[A, C] + [A, B]C
[AB, C] = A[B, C] + [A, C]B