单项选择题
How would you like to pay your bill ?( ) A. By credit card B. What about Mapo Bean Curd? C. Yes ,it is.
How would you like to pay your bill ?( ) A. By credit card B. What about Mapo Bean Curd? C. Yes ,it is.
实对称矩阵，且有
。当k= 时，
必正定。（ ）
A.
1
B.
2
C.
3
D.
4