Sui contributi di Lagrange alla teoria dei numeri

This paper examines Lagrange's contributions to the theory of numbers. Apart from a few isolated results, these contributions fall into two main groups: the first on the foundations of the arithmetical theory of continued fractions and of Diophantine approximation, and the second on the foundations of the arithmetical thery of binary quadratic forms. Special attention is devoted here to Lagrange's contributions to the theory of continued fractions and to the applications of this theory to the approximation of algebraic numbers and to the solution of Diophantine equations, a topic which has not been carefully examined in recent historical studies.