1. The problem statement, all variables and given/known data To show [J2, J+] = 0 2. Relevant equations J+ = Jx + i Jy [J2, Jx ] = 0 [J2, Jy ] = 0 3. The attempt at a solution Step 1: L.H.S. = [J2, J+] Step 2: L.H.S. = [J2, Jx + i Jy ] Step 3: L.H.S. = [J2, Jx ] + i [J2, Jy ] Step 4: L.H.S. = 0 + 0 Step 5: L.H.S. = 0 L.H.S. = R.H.S. I'm kinda confuse about 'Step 3'. Can we take out the 'i' from whole bracket? If yes, then do I have to give any reason for it?