1. The problem statement, all variables and given/known data Two spherical shells of radius ‘a’ and ‘b’ (b>a) are centered about the origin of the axes, and are grounded. A point charge ‘q’ is placed between them at distance R from the origin (a<R<b). Expand the electrostatic potential in Legendre polynomials and find the Green function of the problem as a series. Explicitly find all pre-factors. 2. Relevant equations 3. The attempt at a solution The potential on the outer shell is q/b and the inner shell q/R, right? How do I represent this in legendre polynomials?