数学试题讲解

判断下列矩阵是否是正定矩阵
(1)

A = (\begin{array}{lll} 1 & 1 & 2 \\ 1 & 1 & 0 \\ 2 & 0 & 3 \end{array})

;
(2)

A = (\begin{array}{ccc} 2 & 0 & - 1 \\ 0 & 3 & 0 \\ - 1 & 0 & 2 \end{array})

A. (1)是 , (2)不是 B. (1)是 , (2)是 C. (1)不是 , (2)是 D. (1)不是 , (2)不是