设随机变量X的概率密度函数为<imgwidth="36"height="21"v:shapes="_x0000_i1112"src="http://wljy.whut.edu.cn/uploadfiles/word/xxdsb07.files/image139.png">,且<imgwidth="88"height="27"v:shapes="_x0000_i1113"src="http://wljy.whut.edu.cn/uploadfiles/word/xxdsb07.files/image141.png">,则必有()
①
<imgwidth="36"height="21"v:shapes="_x0000_i1114"src="http://wljy.whut.edu.cn/uploadfiles/word/xxdsb07.files/image139.png">在<imgwidth="50"height="27"v:shapes="_x0000_i1115"src="http://wljy.whut.edu.cn/uploadfiles/word/xxdsb07.files/image144.png">内大于零
②
<imgwidth="36"height="21"v:shapes="_x0000_i1116"src="http://wljy.whut.edu.cn/uploadfiles/word/xxdsb07.files/image139.png">在<imgwidth="50"height="27"v:shapes="_x0000_i1117"src="http://wljy.whut.edu.cn/uploadfiles/word/xxdsb07.files/image147.png">内小于零
③
<imgwidth="90"height="35"v:shapes="_x0000_i1118"src="http://wljy.whut.edu.cn/uploadfiles/word/xxdsb07.files/image149.png">
④
<imgwidth="36"height="21"v:shapes="_x0000_i1119"src="http://wljy.whut.edu.cn/uploadfiles/word/xxdsb07.files/image139.png">在<imgwidth="50"height="27"v:shapes="_x0000_i1120"src="http://wljy.whut.edu.cn/uploadfiles/word/xxdsb07.files/image144.png">上单调增加