Курс математики для нематематических специальностей технических университетов: В 2 т. Т.1. Назаров А.И - 228 стр.

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A·I = I·A = A
I
n
A (m ×n)
I
m
· A = A · I
n
= A
A (m ×n)
B (n × k) C (k × s)
(A · B) · C = A · (B · C).
P = A ·B, Q = B ·C, U = P ·C = (A ·B) ·C, V = A ·Q = A ·(B ·C)
U V (m ×s)
u
ij
=
k
X
r=1
p
ir
c
rj
=
k
X
r=1
Ã
n
X
t=1
a
it
b
tr
!
c
rj
=
k
X
r=1
n
X
t=1
a
it
b
tr
c
rj
;
v
ij
=
n
X
t=1
a
it
q
tj
=
n
X
t=1
a
it
Ã
k
X
r=1
b
tr
c
rj
!
=
n
X
t=1
k
X
r=1
a
it
b
tr
c
rj
;
u
ij
v
ij
¥
A
(m × n) B C (n × k)
A · (B + C) = A · B + A · C.
R = A · (B + C), P = A · B, Q = A · C.
R = P + Q
r
ij
=
n
X
t=1
a
it
(b
tj
+ c
tj
) =
n
X
t=1
a
it
b
tj
+
n
X
t=1
a
it
c
tj
= p
ij
+ q
ij
. ¥