A.a²+3b²≥2(ab+b²)                                         B.a²+3b²＞2(ab+b²)

C.a²+3b²≤2(ab+b²)                                         D.a²+3b²＜2(ab+b²)

①a^bb^a＞a^ab^b  ②a^bb^a＜a^ab^a  ③a^a＜b^b  ④()^a－b＞1

A.①②                 B.②③                   C.①③                      D.②④

A.充要条件                                                     B.必要不充分条件

C.充分不必要条件                                            D.既不充分也不必要条件

A.P≥Q                        B.P≤Q                        C.P＞Q                        D.P＜Q

(2)a²＋b²≥2(a－b－1)；

(3)若a＞b＞c，则bc²＋ca²＋ab²＜b²c＋c²a＋a²b.