In this paper we establish quadratic Lyapunov-like functions for qualitative analysis of switched systems. Specifically, for a class of switched systems consisting of two unstable second-order LTI (linear time-invariant) subsystems, we explore in detail some necessary and sufficient conditions for the existence of common (weakly) quadratic Lyapunov-like functions with associated switching regions in R-2 plane. The existence conditions and the construction of such quadratic Lyapunov-like functions are established by using the conic switching laws.