460
ON THE SYMMETRIC FUNCTIONS OF THE ROOTS
[149
where the cubic function written at full length is
ax 3 + by 3 + cz 3 + 3fy*z + 3gz 2 x + 3hx 2 y + 3iyz 2 4- 3jzx 2 + 3kxy 2 + Qlxyz.
Joining to the system the linear equation
(£ v, y, *) = o,
the linear equations give
x \ y \ z = /3^-yy : 7: ay - /3%,
and the resultant is
(a, b, c, f g, h, i, j, Jc, Z#/3£- yy, y£- a v - /3f) 3 = 0,
which may be represented by
(a, b, c, f, g, h, i, j, k, l$f y, £) 3 = 0,
where the coefficients a, b, &c. are given by means of the Table :—
a
b
c
/
9
h
i
j
k
l
a =
+ f
~3/?y 2
+ 3/3 2 y
b =
-y 3
+ a 3
- 3ya 2
4- 3y 2 a
7*
c =
+ /3 3
-a 3
— 3a/3 2
+ 3a 2 /3
C 3
f =
+ /3y 2
— a 2 /3
+ a 2 /3
-y 2 a
— a 3
— 2a/3y
4- 2ya 2
3^
§ —
+ ya 2
+ a/3 2
+ ^ 2 y
— 2a/3y
+ 2a/3 2
3£ 2 I
h =
+ y 2 a
-/S 2 y
— 2a/3y
-7 3
+w
3^7?
i =
-Fy
+ a 3
+ /3 3
+ 2a/3y
+ a/3 2
— ya 2
— 2a 2 /3
3^ 2
j =
-y 2 a
4- 2a/3y
— a/3 2
+ /V
-2/8 2 y
3CI 2
k=
-a 2 />
+ 2a/3y
+ y 3
+ ya 2
-/3y 2
— 2y 2 a
3^
1 =
— ya 2
-a/3 2
~/V
4- a 2 /3
+ ^ 2 y
4- y 2 a
viz. a = by 3 — c/3 3 — 3f(3y 2 + 3i/3 2 y, &c.
But if the roots of the given system are
(«1» Vu *i), ( x 2, y„ z 9 ), Os, y s , z 3 ),
then the resultant of the three equations may also be represented by
Oi> yi, ^51, y, £)•(**, ya» *»££, y, 0-(^3,2/3, ^11, t?, 0;
and comparing with the former expression, we find :
cL ■— 0C-]0C<2pCfo
b = 2/12/22/3,
c = Z-^Z^Z^