设随机变量<imgwidth="110"height="25"v:shapes="_x0000_i1125"src="http://wljy.whut.edu.cn/uploadfiles/word/xxdsb09.files/image167.png">为独立同分布序列,且<imgwidth="92"height="25"v:shapes="_x0000_i1126"src="http://wljy.whut.edu.cn/uploadfiles/word/xxdsb09.files/image169.png">服从参数为<imgwidth="15"height="19"v:shapes="_x0000_i1127"src="http://wljy.whut.edu.cn/uploadfiles/word/xxdsb09.files/image171.png">的指数分布,则下面式子中正确的是()
①
<imgwidth="173"height="90"v:shapes="_x0000_i1128"src="http://wljy.whut.edu.cn/uploadfiles/word/xxdsb09.files/image173.png">
②
<imgwidth="191"height="90"v:shapes="_x0000_i1129"src="http://wljy.whut.edu.cn/uploadfiles/word/xxdsb09.files/image175.png">
③
<imgwidth="192"height="90"v:shapes="_x0000_i1130"src="http://wljy.whut.edu.cn/uploadfiles/word/xxdsb09.files/image177.png">
④
<imgwidth="192"height="90"v:shapes="_x0000_i1131"src="http://wljy.whut.edu.cn/uploadfiles/word/xxdsb09.files/image179.png">