On Bernstein and Turán-type integral mean estimates for polar derivative of a polynomial

Let $p(z)$ be a polynomial of degree n having no zero in $|z|< k$ , $k\leq 1$ , then Govil [Proc. Nat. Acad. Sci., 50(1980), 50-52] proved $$ \max _{|z|=1}|p'(z)|\leq \frac{n}{1+k^{n}}\max _{|z|=1}|p(z)|, $$ provided $|p'(z)|$ and $|q'(z)|$ attain their maxima at the same point on the circle $|z|=1$ , where $$ q(z)=z^{n}\overline{p\bigg(\frac{1}{\overline{z}}\bigg)}. $$ In this paper, we present integral mean inequalities of Turán- and Erdös-Lax-type for the polar derivative of a polynomial by involving some coefficients of the polynomial, which refine some previously proved results and one of our results improves the above Govil inequality as a special case. These results incorporate the placement of the zeros and some coefficients of the underlying polynomial. Furthermore, we provide numerical examples and graphical representations to demonstrate the superior precision of our results compared to some previously established results.

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Publication Details

Journal
Journal of Inequalities and Applications
Published
2024-08-26
DOI
https://doi.org/10.1186/s13660-024-03183-5
Citations
2
Primary Topic
Mathematical functions and polynomials
Type
article
Field-Weighted Citation Impact
1.95

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article

On Bernstein and Turán-type integral mean estimates for polar derivative of a polynomial

Barchand Chanam, Khangembam Babina Devi
2 citations
Journal of Inequalities and Applications
Mathematical functions and polynomials
1.95
article

On Bernstein and Turán-type integral mean estimates for polar derivative of a polynomial

Barchand Chanam, Khangembam Babina Devi
article en
2 citations

Abstract

Let $p(z)$ be a polynomial of degree n having no zero in $|z|< k$ , $k\leq 1$ , then Govil [Proc. Nat. Acad. Sci., 50(1980), 50-52] proved $$ \max _{|z|=1}|p'(z)|\leq \frac{n}{1+k^{n}}\max _{|z|=1}|p(z)|, $$ provided $|p'(z)|$ and $|q'(z)|$ attain their maxima at the same point on the circle $|z|=1$ , where $$ q(z)=z^{n}\overline{p\bigg(\frac{1}{\overline{z}}\bigg)}. $$ In this paper, we present integral mean inequalities of Turán- and Erdös-Lax-type for the polar derivative of a polynomial by involving some coefficients of the polynomial, which refine some previously proved results and one of our results improves the above Govil inequality as a special case. These results incorporate the placement of the zeros and some coefficients of the underlying polynomial. Furthermore, we provide numerical examples and graphical representations to demonstrate the superior precision of our results compared to some previously established results.

Journal of Inequalities and ApplicationsVol. 2024(1)
National Institute of Technology Manipur (IN)
Council of Scientific and Industrial Research, India
Openalex Percentile: Top 15%
Mathematical functions and polynomials
1.95
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