二次型矩阵<imgwidth="110"height="114"v:shapes="_x0000_i1347"src="http://wljy.whut.edu.cn/uploadfiles/word/xxds05.files/image430.png">的正惯性指数为(
①
<imgwidth="14"height="20"v:shapes="_x0000_i1348"src="http://wljy.whut.edu.cn/uploadfiles/word/xxds05.files/image428.png">
②
<imgwidth="10"height="18"v:shapes="_x0000_i1349"src="http://wljy.whut.edu.cn/uploadfiles/word/xxds05.files/image323.png">
③
<imgwidth="14"height="18"v:shapes="_x0000_i1350"src="http://wljy.whut.edu.cn/uploadfiles/word/xxds05.files/image426.png">
④
<imgwidth="14"height="18"v:shapes="_x0000_i1351"src="http://wljy.whut.edu.cn/uploadfiles/word/xxds05.files/image433.png">