1. The problem statement, all variables and given/known data Consider A(x) is an arbitrary function of x, and px is the momentum operator. Show that they satisfy the following condition: [px,A(x)] = (-i/ħ)*d/dx(A(x)) where [px,A(x)] = pxA(x) - A(x)px 2. Relevant equations ħ = h/2π px = (-iħ)d/dx 3. The attempt at a solution Starting with the expression given at the bottom of the question and subbing in the expression for the momentum operator and factoring out -iħ, I get: [px,A(x)] = -iħ*(d/dx(A(x)) - A(x)d/dx) and I'm stuck there for the time being... I don't really understand how to get ħ into the denominator or what to do with the term in brackets. Any help would be appreciated.