A problem of I. Raşa on Bernstein polynomials and convex functions

Abstract: We present an elementary proof of a conjecture by I. Ra\c{s}a which is an inequality involving Bernstein basis polynomials and convex functions. It was affirmed in positive very recently by the use of stochastic convex orderings. Moreover, we derive the corresponding results for Mirakyan-Favard-Sz\'asz operators and Baskakov operators.