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Born Sept. 23, 1765, in Valentano, near Viterbo; died May 10, 1822, in Modena. Italian mathematician.
Ruffini published in 1804 a method for the approximate calculation of the real roots of algebraic equations, which was rediscovered in 1819 by the English mathematician W. Horner. In 1799 he gave the first proof that the general algebraic equation of degree five cannot be solved by radicals; his proof, however, was not rigorous. Ruffini also worked out a number of ideas of the theory of finite substitution groups.