The letters next to p and L should be subscripts. [Lz, px] = [xpy − ypx, px] = [xpy, px] − [ypx, px] = py[x, px] −0 = i(hbar)py 1.In this calculation, why is [x, px] not 0 even they commute? 2.Why is py put on the left instead of the right in the second last step? i thought it should be put on the right bec it's on the right of x in the third step, and we have to keep the orders for operators. 3.With L=rxp, why are we multiplying i(hbar) instead of multiplying by i/ (hbar), coz at the beginning, we change all the d/dx or d/dy or d/dz to px, py, pz, why aren't we multiplying i/(hbar) to compensate what we change for convenient calculation?