ON THE SUMS OF TWO CUBES

We solve the equation f(x, y)3 + g(x, y)3 = x3 + y3 for homogeneous f, g ∈ ℂ(x, y), completing an investigation begun by Viete in 1591. The usual addition law for elliptic curves and composition give rise to two binary operations on the set of solutions. We show that a particular subset of the set of solutions is ring isomorphic to ℤ[e2πi/3].