A “SMITH’S PRIZE” PAPERO; SOLUTIONS.
[From the Oxford, Cambridge and Dublin Messenger of Mathematics, vol v. (1870),
pp. 182—203.]
1. Mention what form of given relation <j> (a, b, c, ...) = 0 between the roots of a
given equation will in general serve for the rational determination of the roots; explain
the case of failure; and state what information as to the roots is furnished by a given
relation not of the form in question.
In the given relation, (a, b, c,...) must be a wholly unsymmetrical function of
the roots; that is, a function altered by any permutation whatever of the roots; or,
what is the same thing, by any interchange whatever of two roots.
For this being so, if a, /3, 7,... be the values of the roots, then for some one
order, say a, ¡3, 7,..., of these values the given relation <£ (a, b, c, ...) = 0 will be satisfied
by writing therein a = a, b — /3, c = 7, &c.; but it will in general be satisfied for this
order only, and not for any other order whatever (viz. it will not be satisfied by
writing a = /3, b = a, c = 7, &c., or by any other such system). The given equation
determines that the roots are equal to a, /3, 7, ... in some order or other, but the given
equation combined with the given relation <£ (a, b, c, ...) = 0, determines that a is = a
and not equal to any other value, b = ¡3 and not equal to any other value, &c.; and
it thus appears a priori, that the two together must rationally determine each of the
roots a, b, c,...; the a posteriori verification, and actual rational determination of the
values of a, b, c,... respectively, is a separate question which is not here considered.
The function (f)(a, b, c,...) may be of the proper form, and yet the particular
values a, /3, 7,... be such that the given relation 0 (a, b, <?,...) = 0 is satisfied, not only
for the single arrangement a —a, b = /3, c = y, &c., but for some other arrangement,
1 Set by me for the Master of Trinity, Feb. 3, 1870.