ai and bi(i=1,...,n) ,the assets modeled with Expected Utility Theory.
对任意的i，ai~bi and ri属于(0,1), ri(i=1到n的加和)= 1.
prove the below with the axioms like completeness, Reflexivity, Transivity, Continuity, Independence:   
riai(i=1到n的加和)~ribi(i=1到n的加和)