判断下列矩阵是否是正定矩阵
(1) $A =\left(\begin{array}{lll}1 & 1 & 2 \\ 1 & 1 & 0 \\ 2 & 0 & 3\end{array}\right)$;
(2) $A =\left(\begin{array}{ccc}2 & 0 & -1 \\ 0 & 3 & 0 \\ -1 & 0 & 2\end{array}\right)$.
A
(1)是 , (2)不是
B
(1)是 , (2)是
C
(1)不是 , (2)是
D
(1)不是 , (2)不是
E
F