. V 3 (x, y, z), k ( ) , (12), A .
, , . (12) . C (x ¢, y ¢, z ¢), A ¢ k ( ) . A A ¢
A ¢= C AC. (11)
, C , .. C = C -1; A ¢= C -1 AC. . (10) , A: V 3 V 3 A (x, y, z). k ( ) (.. ). A , A .
A (5) B ¢= {, , }. , - (x ¢, y ¢, z ¢), , , ,
k ( ) =l1 x ¢2 + l2 y ¢2 + l3 z ¢2 (13)
(x, y, z) (x ¢, y ¢, z ¢):
X ¢= C -1 X, (14)
:
X = C X ¢, (14¢)
C , X X ¢ :
X =, X ¢=.
, B = {, , } B ¢= {, , }
= c 11 + c 12 + c 13,
= c 21 + c 22 + c 23, (15)
= c 31 + c 32 + c 33,
C :
C =, (16)
(14¢) :
x = c 11 x ¢ + c 21 y ¢ + c 31 z ¢,
y = c 12 x ¢ + c 22 y ¢ + c 32 z ¢, (14¢)
z = c 13 x ¢ + c 23 y ¢ + c 33 z ¢.
, . , , C , .. C = C -1. (14) X ¢= C X :
x ¢= c 11 x + c 12 y + c 13 z,
y ¢= c 21 x + c 22 y + c 23 z,
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z ¢= c 31 x + c 32 y + c 33 z.
, , (14¢), .
3. V 3 k () (x, y, z)
k ( ) = 3 y 2 + 4 xy - 2 xz - 4 yz.
(x ¢, y ¢, z ¢) k () .
. k () (x, y, z). 3 = a 22, 4 = 2 a 12, -2 = 2 a 13, - 4 = 2 a 23, .. x 2 y 2 , a 11= a 33 = 0. ,
A =.
, A 2,
l1 = -1,,
l2 = -1,,
l3 = 5,,
, (x ¢, y ¢, z ¢) , B ¢= {, , }, k ( )
k () = - x ¢2 - y ¢2 + 5 z ¢2.
:
x ¢= x + z,
y ¢= x - y - z,
z ¢= x + y - z,
:
x = x ¢ + y ¢ + z ¢,
y = - y ¢ + z ¢, (17)
z = x ¢ - y ¢ - z ¢,