N
A.
1
) + rank(A
2
rank(A
n
).
a :E
1
E
2
i
E
1
2
E
n
A
n + 1
A
1
A
2
n+1
= 0 suy ra
A A
1
A
2
A
n+1
A
1
A
2
.
b :
a, rank(B).
B).
A/B
c c + B
} = C/B
A/B.
rank(C) rank(A/B).
B C
e
A.
rank(A) rank(B) + rank(C)
2
= 0 l.ann(A) n r.ann(A) hay
l.ann(A)r.ann(A)
(AX)
2
= 0 r.ann(A) m l.ann(A) hay
r.ann(A)l.ann(A)
r.ann(A) = l.ann(A).
ann(A)
2
= 0
ann(A) .
c.B ann(A)
B.
d,
R
A
R
) A
A.
A
ann(A) = ann(A
n
sao cho
A
1
A
2
e
R
R
R
.
i
= ann(A
i
i
P
i