Question

under what conditions the product of the convex functions is convex? under these conditions prove this fact.​

Answer 1

Answer:

Theorem 1. A function f : Rn → R is convex if and only if the function g : R → R given by g(t) = f(x + ty) is convex (as a univariate function) for all x in domain of f and all y ∈ Rn. (The domain of g here is all t for which x + ty is in the domain of f.)