[SOLVED] Kernel "stable under": is my interpretation correct? 1. The problem statement, all variables and given/known data A1, A2, A3,..., Ar are endomorphisms. W is the kernel of Ar - lambda*I, where lambda is the eigenvalue of Ar. W is stable under A1, A2, A3,..., Ar-1. Question: does "stable under" equal "closed under", and is the following interpretation of this stability correct? For all elements u in W, Aku is an element in W.