Аңдатпа
Several extremal problems on the best mean-square approximation of the functions 𝑓, on a semiaxis with a power-law weight are solved in the paper, which can be applied in solving various problems. Exact Jackson–Stechkin-type inequalities are obtained for some classes of functions in which the values of the best approximations are estimated from above in terms of 𝑘-th order Hankel moduli of smoothness.