Abstract. M. Frentiu defined certain linear combinations of Szász--Mirakjan operators. In the case of $2r$-times $(r>1)$ differentiable functions, these linear combinations provide a better approximation than the original operator. In this paper we show that this method can be applied to a certain extension of Szász--Mirakjan operators that has been introduced in [3], in order to obtain an approximation on the whole real axis.

AMS Subject Classification (1991): 41A35

Received October 2, 1994. (Registered under 5638/2009.)