题目内容
（请给出正确答案）
[主观题]
证明：rank（A+B)≤rank（A)+rank（B)．
提问人：网友garlic11
发布时间：2022-01-07
如搜索结果不匹配，请 
A、SELECT rank, AVG(salary) FROM people HAVING AVG(salary) > 1000 GROUP BY rank;
B、SELECT rank, AVG(salary) FROM people GROUP BY rank HAVING AVG(salary) > 1000
C、SELECT AVG(salary) FROM people GROUP BY rank HAVING AVG(salary) > 1000;
D、SELECT rank, AVG(salary) FROM people GROUP BY rank WHERE AVG(salary) > 1000;
，E为单位矩阵，A*为A的伴随矩阵，则B＝______．
为齐次微分方程组
的基本解组，试求aij(t)，i，j=1，2．
