设二次型<img src="/lqwvjeImg/c5/c5251a80293eeaa1a15d045b2569475b.png"style="width:251px;height:24px;"> ,则( ) .<br>·<img src="/lqwvjeImg/5b/5b06055f94b441cce02dd972e27dfc26.png"style="width:16px;height:20px;">为正定的<br>·<img src="/lqwvjeImg/5b/5b06055f94b441cce02dd972e27dfc26.png"style="width:16px;height:20px;">为负定的<br>·<img src="/lqwvjeImg/5b/5b06055f94b441cce02dd972e27dfc26.png"style="width:16px;height:20px;">的秩为1<br>·<img src="/lqwvjeImg/5b/5b06055f94b441cce02dd972e27dfc26.png"style="width:16px;height:20px;">的秩为 2