1. The problem statement, all variables and given/known data In the Lectures, we are told that techniques like homogeneity and superposition work only for linear circuits, but in Chapter 3 of the Textbook (which is the only place I can find one) I see a definition of linearity as "A circuit is linear if and only if 2. Relevant equations f(ax1 + bx2) = af(x1) + bf(x2)" i.e. if homogeneity and superposition work for it. 3. The attempt at a solution How do I tell, when confronted with an arbitrary circuit, whether or not it is linear - whether or not homogeneity and superposition are going to work for it?