【单选题】
实二次型<imgwidth="170"height="28"v:shapes="_x0000_i1222"src="http://wljy.whut.edu.cn/uploadfiles/word/xxds05.files/image226.png">为正定的充要条件是()
①
<imgwidth="18"height="24"v:shapes="_x0000_i1223"src="http://wljy.whut.edu.cn/uploadfiles/word/xxds05.files/image228.png">的秩为<imgwidth="14"height="16"v:shapes="_x0000_i1224"src="http://wljy.whut.edu.cn/uploadfiles/word/xxds05.files/image188.png">
②
<imgwidth="18"height="24"v:shapes="_x0000_i1225"src="http://wljy.whut.edu.cn/uploadfiles/word/xxds05.files/image228.png">的正惯性指数为<imgwidth="14"height="16"v:shapes="_x0000_i1226"src="http://wljy.whut.edu.cn/uploadfiles/word/xxds05.files/image188.png">
③
<imgwidth="18"height="24"v:shapes="_x0000_i1227"src="http://wljy.whut.edu.cn/uploadfiles/word/xxds05.files/image228.png">的正惯性指数等于<imgwidth="18"height="24"v:shapes="_x0000_i1228"src="http://wljy.whut.edu.cn/uploadfiles/word/xxds05.files/image228.png">的秩
④
<imgwidth="18"height="24"v:shapes="_x0000_i1229"src="http://wljy.whut.edu.cn/uploadfiles/word/xxds05.files/image228.png">的负惯性指数为<imgwidth="14"height="16"v:shapes="_x0000_i1230"src="http://wljy.whut.edu.cn/uploadfiles/word/xxds05.files/image188.png">