We investigate certain positive linear operators L_n preserving the functions e_k (x)=x^k, k=0, 1, and modified operators L_n^* which preserve e_0 and e_2. We show that the error of approximation of f by L_n^* (f) is smaller than for L_n(f).
REMPULSKA, LUCYNA and TOMCZAK, KAROLINA
"Approximation by certain linear operators preserving x^2,"
Turkish Journal of Mathematics: Vol. 33:
3, Article 8.
Available at: https://journals.tubitak.gov.tr/math/vol33/iss3/8