设离散的随机变量X的分布为<imgwidth="222"height="27"v:shapes="_x0000_i1155"src="http://wljy.whut.edu.cn/uploadfiles/word/xxdsb07.files/image211.png">则<imgwidth="27"height="19"v:shapes="_x0000_i1156"src="http://wljy.whut.edu.cn/uploadfiles/word/xxdsb07.files/image213.png">()
①
<imgwidth="32"height="19"v:shapes="_x0000_i1157"src="http://wljy.whut.edu.cn/uploadfiles/word/xxdsb07.files/image215.png">
③
<imgwidth="35"height="41"v:shapes="_x0000_i1158"src="http://wljy.whut.edu.cn/uploadfiles/word/xxdsb07.files/image217.png">
④
<imgwidth="35"height="41"v:shapes="_x0000_i1159"src="http://wljy.whut.edu.cn/uploadfiles/word/xxdsb07.files/image219.png">