- Two invariants, two quartics and a
**sextic**. They are connected by the relation 212 = 2 i f?0 - D3 -3 jf 3. - The .
**sextic**covariant t is seen to be factorizable into three quadratic factors 4 = x 1 x 2, =x 2 1 - 1 - 2 2, 4) - x, which are such that the three mutual second transvectants vanish identically; they are for this reason termed conjugate quadratic factors. - Three quintic forms f; (f, i) 1; (i 2, T)4 two
**sextic**forms H; (H, 1)1 one septic form (i, T)2 one nonic form T. - For a further discussion of the binary
**sextic**see Gordan, loc. cit., Clebsch, loc. cit. - The complete systems of the quintic and
**sextic**were first obtained by Gordan in 1868 (Journ.

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