Abstract
We prove theorems that characterize the classes of functions whose best approximations by algebraic polynomials tend to zero with given order. We construct approximations of solutions of operator-differential equations by polynomials in the inverse operator.
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Translated from Ukrainskii Matematicheskii Zhurnal, Vol. 50, No. 11, pp. 1506–1516, November, 1998.
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Kashpirovskii, O.I., Mitnik, Y.V. Approximation of solutions of operator-differential equations by operator polynomials. Ukr Math J 50, 1719–1730 (1998). https://doi.org/10.1007/BF02524478
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DOI: https://doi.org/10.1007/BF02524478