二次型<imgwidth="230"height="28"v:shapes="_x0000_i1248"src="http://wljy.whut.edu.cn/uploadfiles/word/xxds05.files/image251.png">的秩为()
①
<imgwidth="38"height="18"v:shapes="_x0000_i1249"src="http://wljy.whut.edu.cn/uploadfiles/word/xxds05.files/image253.png">
②
<imgwidth="42"height="18"v:shapes="_x0000_i1250"src="http://wljy.whut.edu.cn/uploadfiles/word/xxds05.files/image255.png">
③
<imgwidth="40"height="20"v:shapes="_x0000_i1251"src="http://wljy.whut.edu.cn/uploadfiles/word/xxds05.files/image257.png">