设向量组\( {\left( {2,1,1,1} \right)^T},{\left( {2,1,a,a} \right)^T},{\left( {3,2,1,a} \right)^T},{\left( {4,3,2,1} \right)^T} \) 线性相关，且\( a \ne 1 \) ，则 \( a = \)______

“____ he have left yesterday?” Yes, he ____<br/>yesterday.” No, he ____ yesterday.” A: Must; must have left; can’t have left B: Can; can have<br/>left; can’t have left C: Can; must have left; can’t have left D: May; must<br/>have left; shouldn’t have left

设`\A`是`\m \times n`矩阵，`\m` 小于 `\n`，则必有 （ ） A: \[\left| {{A^T}A} \right| \ne 0\] B: \[\left| {{A^T}A} \right| = 0\] C: \[\left| {A{A^T}} \right| &gt; 0\] D: \[\left| {A{A^T}} \right| &lt; 0\]

设\( A,\;B \) 均为\( n \) 阶方阵，则必有（ ）. A: \( {(A + B)^2} = {A^2} + 2AB + {B^2} \) B: \( \left| {A + B} \right| = \left| A \right| + \left| B \right| \) C: \( \left| {AB} \right| = \left| A \right|{\kern 1pt} \left| B \right| \) D: \( {\left( {AB} \right)^{\rm T}} = {A^{\rm T}}{B^{\rm T}} \)

Hasn't the rain ______ yet? A: left off B: left behind C: left over D: left away

设\( \alpha {\rm{ = }}{\left( {1,0,1} \right)^T},\,A = \alpha {\alpha ^T} \)，则\( \left| A \right|{\rm{ = }} \)______

程序填空，输出下面图形 import turtle as t t.pensize(2) for i in range( ？ ): t.fd(150) t.left( ？ )https://p.ananas.chaoxing.com/star3/origin/da5f4ed9d27398da8322ee6441e5c8f2.png

设 \( A \)为方阵，则 \( \left| { { A^T}} \right| = \,\left| A \right|\, \).（ ）

设 \( A \)为 \( m \times n \)矩阵， \( B \)为 \( n \times m \)矩阵，则下列结论中不正确的是（ ） A: \( {\left( {AB} \right)^T} = {B^T}{A^T} \) B: \( \left| {AB} \right| = \left| {BA} \right| \) C: \( tr\left( {AB} \right) = tr\left( {BA} \right) \) D: \( {A^T}A,\;B{B^T} \)均为\(n\)阶对称阵

He ( ) the school. His cellphone is still on the desk. A: mustn't have left B: can't leave C: needn't leave D: can't have left