please prove this question

Let f1 : R" > R and f2 : R\" > R be two functions. (5.1) Consider the following proposition: If epi(f1) epi(f2) is a convex set, then at least one of the functions f1 and f2 is a convex function. Either prove this proposition or give a counterexample (i.e., nd two functions f1 : R\" > R and f2 : R\" > R that satisfy the hypothesis but do not satisfy the conclusion)