for a project I need to prove quasiconvexity of several general functions. Can I argue that the union (or sum, or difference...) of quasiconvex functions is again quasiconvex? I do know that the sum of convex functions is again convex, does this apply to quasiconvexity?
My functions may include the log-function, which is quasiconvex but not convex (for example).
Thank you very much for your help.
Best wishes, Britta