Direct and converse results for linear combinations of Baskakov-Durrmryer operators

We consider the linear combinations of Baskakov-Durrmeyer operators and give the characterization in terms of the classical modulous of smoothness for ∞-norm by the means of the pointwise simultanrous approximation. An equivalence ralation between the derivatives of these operators and smoothness of functions is also presented. Supported by Zhejiang Provincial Foundation of China.