For three variables, α, β, γ, the elementary symmetric polynomials are
These expressions generalize naturally to n variables, with σk being the sum of the products of k of the variables. The elementary symmetric polynomials appear in Viète’s formulae.
The elementary symmetric polynomials are symmetric functions, and any symmetric polynomial can be expressed in terms of the elementary symmetric polynomials. For example, if sk = αk + βk + γk, then
gives a general recursive means of expressing sk in terms of σ1,σ2,…,σk. See Newton’s identities.