Generalizations of some inequalities for rational functions with prescribed poles and restricted zeros

被引:0
作者
Preeti Gupta
Sunil Hans
Abdullah Mir
机构
[1] Amity University,Department of Applied Mathematics
[2] University of Kashmir,Department of Mathematics
来源
Analysis and Mathematical Physics | 2022年 / 12卷
关键词
Rational functions; Inequalities; Polar derivative; Restricted zeros; Poles; 26A84; 26D07;
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摘要
The main purpose of this paper is to established the modulus of derivative of rational functions r(z) having all its zeros in |z|≤k≤1,\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$|z|\le k \le 1,$$\end{document} except two zeros z0\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$z_{0}$$\end{document} and z1\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$z_{1}$$\end{document} of multiplicity μ\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\mu $$\end{document} and ν\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\nu $$\end{document} respectively and some other related inequalities. The obtained results generalize and sharpen some well-known inequalities for the derivative of rational functions with prescribed poles and in turn produces some results besides the refinements of some polynomial inequalities as well.
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