693]
A TENTH MEMOIR ON QUANTICS.
357
a new quintic, which is the canonical form in question : the covariants hereof
(reckoning the quintic itself as a covariant) will be written A, B, C,..,V, W, and
will be spoken of as capital covariants.
376. The fundamental property is : Every capital covariant, say I, has for its
leading coefficient the corresponding covariant i multiplied by a power of a : and
this follows as an immediate consequence of the foregoing genesis of A. The
covariant i of the form
i(a, b, c, d, e, f$£ y) 5
d
has a leading coefficient
= ^ (a 2 cf — a 2 de + &c.),
a 4 v 7
which, when a, b, c, d, e, f .., i denote leading coefficients, is = i multiplied by a power
of a: and upon substituting for the quintic the linear transformation thereof
(1, 0, c, / a?b — 3c 2 , a 2 e-2c/$£, y) 5 ,
(observing that, in the transformation |, y into £ — by, ay, the determinant of sub
stitution is = a), the value is still = i multiplied by a power of a ; or using the
relation a = a, say the value is —i multiplied by a power of a. Now the covariant
i is the same function of the covariants a, b, c, d, e, f that the leading coefficient
i is of the leading coefficients a, b, c, d, e, /; hence, the italic letters now denoting
covariants, the leading coefficient still is =i multiplied by a power of a: which
is the above-mentioned theorem.
377. To show how the transformation is carried out, consider, for example, the covariant
B. This is obtained from the corresponding covariant of (a, b, c, d, e, f$£, y) 5 , that is,
ae
1
af
1
bf
1
bd
- 4
be -
- 3
ce
- 4
c 2
+ 1
cd + 1
d 2
+ 3
by changing the variables, and for the coefficients
a, b, c, d, e, f
writing
1, 0, c, /, a-b — 3c 2 , a 2 e — 2c/;
thus the coefficients are
First.
1 (a 2 6 - 3c 2 )
+ 3c 2
= ad)
Second.
1 (u 2 e — 2c/)
+ 2 of
= a?e
Third.
— 4 c (a-b — 3c 2 )
+ 3/ 2
= — 4a 2 6c + 12c 3
+ 3 (— a 3 d + a 2 bc — 4c 3 )
= a 2 (— Sad — be) ;