答案：
第1空:
答案：
第1空:
A. 4
B. 5
C. 6
D. 7
矩阵,如果 INCLUDEPICTURE ＼d "http://mooc1-2.chaoxing.com/ananas/latex/p/312248" ＼* MERGEFORMATINET 
,则( )
A. INCLUDEPICTURE ＼d "https://p.ananas.chaoxing.com/star3/origin/22036fe43827ed0db23d177e31c3a2b4.png" ＼* MERGEFORMATINET 
B. INCLUDEPICTURE ＼d "https://p.ananas.chaoxing.com/star3/origin/b2438085c7f52fc89bd82d931934be3d.png" ＼* MERGEFORMATINET 
C. INCLUDEPICTURE ＼d "https://p.ananas.chaoxing.com/star3/origin/5bfacced11915d1e48dda63d54b5fc24.png" ＼* MERGEFORMATINET 
D. INCLUDEPICTURE ＼d "https://p.ananas.chaoxing.com/star3/origin/33a779319651bcd1abbd76889f388a9f.png" ＼* MERGEFORMATINET 
,|b|=2,且( )⊥a,则向量a和b的夹角是________度.
A. INCLUDEPICTURE ＼d "https://p.ananas.chaoxing.com/star3/origin/cbfa63facc47534b5791c0edb3985858.png" ＼* MERGEFORMATINET 
B. INCLUDEPICTURE ＼d "https://p.ananas.chaoxing.com/star3/origin/f00401a0806543e0c700b626719028d3.png" ＼* MERGEFORMATINET 
C. INCLUDEPICTURE ＼d "https://p.ananas.chaoxing.com/star3/origin/b68a546fa6a2abd42fdf096156b763f0.png" ＼* MERGEFORMATINET 
D. INCLUDEPICTURE ＼d "https://p.ananas.chaoxing.com/star3/origin/d7b17fc70b316cb4a0d33d9111f5a0fe.png" ＼* MERGEFORMATINET 
A. z=ABx
B. z=BAx
C. x=ABz
D. x=BAz
矩阵,齐次线性方程组 INCLUDEPICTURE ＼d "http://mooc1-2.chaoxing.com/ananas/latex/p/181683" ＼* MERGEFORMATINET 
仅有零解的充要条件是 INCLUDEPICTURE ＼d "http://mooc1-2.chaoxing.com/ananas/latex/p/53238" ＼* MERGEFORMATINET 
A. 小于m
B. 小于n
C. 等于m
D. 等于n
A. e是割点
B. {a, e}是点割集
C. {b, e}是点割集
D. {d}是点割集
