One of the most important chapters in modern functional analysis is the
theory of approximate methods for solution of various mathematical
problems. Besides providing considerably simplified approaches to
numerical methods, the ideas of functional analysis have also given rise
to essentially new computation schemes in problems of linear algebra,
differential and integral equations, nonlinear analysis, and so on. The
general theory of approximate methods includes many known fundamental
results. We refer to the classical work of Kantorovich; the
investigations of projection methods by Bogolyubov, Krylov, Keldysh and
Petrov, much furthered by Mikhlin and Pol'skii; Tikho- nov's methods for
approximate solution of ill-posed problems; the general theory of
difference schemes; and so on. During the past decade, the Voronezh
seminar on functional analysis has systematically discussed various
questions related to numerical methods; several advanced courses have
been held at Voronezh Uni- versity on the application of functional
analysis to numerical mathe- matics. Some of this research is summarized
in the present monograph. The authors' aim has not been to give an
exhaustive account, even of the principal known results. The book
consists of five chapters.