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Results on the deficiencies of some differential-difference polynomials of meromorphic functions

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Zheng X.-M., Xu H.-Y.

Open Mathematics

2016

tom 14

nr 1

100-108

In this paper, we study the relation between the deficiencies concerning a meromorphic function f(z), its derivative f′(z) and differential-difference monomials f(z)mf(z+c)f′(z), f(z+c)nf′(z), f(z)mf(z+c). The main results of this paper are listed as follows: Let f(z) be a meromorphic function of finite order satisfying lim sup r→+∞ T(r, f) T(r, f ′ ) <+∞, $$\mathop {\lim \,{\rm sup}}\limits_{r \to + \infty } {{T(r,\,f)} \over {T(r,\,f')}}{\rm{ < }} + \infty ,$$ and c be a non-zero complex constant, then δ(∞, f(z)m f(z+c)f′(z))≥δ(∞, f′) and δ(∞,f(z+c)nf′(z))≥ δ(∞, f′). We also investigate the value distribution of some differential-difference polynomials taking small function a(z) with respect to f(z).

Ograniczanie wyników

1 Open Mathematics

1 Xu H.-Y.

1 Zheng X.-M.

1 2016

Wyniki wyszukiwania

Results on the deficiencies of some differential-difference polynomials of meromorphic functions