... cdacluingtoiIll.nghienC1111v"ecac ham chon.Cacham chonIll.cac mo tatu'ong dirongcda ho cac phu thuoc ham.Trongbal bao naychiingtc5itrlnh bay m9t so cac tinh cMt co-bin lien quan dgn cac ham chon.1. INTRODUCTIONThe ... a choice function, if everyAEP(U)'thenC(A) ~ A.Uis interpreted as a set of alternatives,Aas a set of alternatives given to the decision-maker tochoose the best andC(A)as a choice ... A),H(A)=AnL(U-A).(*)(**)We can easily prove thatC(A)andH(A)are two choice functions. And we nameC(A)choicefunction-I (for short, CF-I), and H(A) choice function-II (for short, CF-II).Theorem2.8.The...