F(x,y)=xy is convex or concave? Nonconvex Dec 29, 2020 E Edgar Dec 29, 2020 #1 f(x,y)=xy is convex or concave? E Erling D.Andersen Dec 29, 2020 #2 It is neither I am afraid. E Edgar Dec 29, 2020 #3 Replying to #2 Thank you,I have understood.But I want to transfer f(x,y)=xy into a convex function,what to do about it ?Because CVX doesn’t recognize this function. M Mark L. Stone Dec 29, 2020 #4