随机试验E有三种两两不相容的结果A1,A2,A3,且三种结果发生的概率均为,将试验E独立重复2次,X表示2次试验中结果A1发生的次数,Y表示2次试验中结果A2发
A -<img width="20" height="52" src="https://www.beizhujiaoyu.com/uploads/202208/20210519002323_0226.gif" /> B -<img width="18" height="52" src="https://www.beizhujiaoyu.com/uploads/202208/20210519002324_9601.gif" /> C <img width="18" height="52" src="https://www.beizhujiaoyu.com/uploads/202208/20210519002324_9601.gif" /> D <img width="20" height="52" src="https://www.beizhujiaoyu.com/uploads/202208/20210519002323_0226.gif" />