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I nternational Journal Of Computational Engineering Research (ijceronline.com) Vol. 3 Issue.1

On The Enestrom –Kakeya Theorem and Its Generalisations 1,

M. H. Gulzar

1,

Department of Mathematics University of Kashmir, Srinagar 190006

Abstract Many extensions of the Enestrom –Kakeya Theorem are availab le in the literature. In this paper we prove some results which generalize some known results .

Mathematics Subject Classification:

30C10,30C15

Key-Words and Phrases : Comp lex nu mber, Polynomial , Zero, Enestrom – Kakeya Theorem 1. Introduction And Statement Of Results The Enestrom –Kakeya Theorem (see[7]) is well known in the theory of the distribution of zeros of polynomials and is often stated as follo ws: n

Theorem A: Let

P( z )   a j z j be a polynomial of degree n whose coefficients satisfy j 0

an  an1  ......  a1  a0  0 . Then P(z) has all its zeros in the closed unit disk

z  1.

In the literature there exist several generalizations and extensions of this resu lt. Joyal et al [6] extended it to polynomials with general monotonic coefficients and proved the following result: n

Theorem B : Let

P( z )   a j z j be a polynomial of degree n whose coefficients satisfy j 0

an  an1  ......  a1  a0 . Then P(z) has all its zeros in

z 

a n  a0  a0 an

.

Aziz and zargar [1] generalized the result of Joyal et al [6] as follows: n

Theorem C: Let

P( z )   a j z j be a polynomial of degree n such that for some k  1 j 0

kan  an1  ......  a1  a0 . Then P(z) has all its zeros in

z  k 1 

kan  a0  a0 an

.

For polynomials ,whose coefficients are not necessarily real, Govil and Rahman [2] proved the following generalization of Theorem A : n

Theorem C: If

P( z )   a j z j is a polyno mial of degree n with Re( a j )   j and Im(a j )   j , j=0,1,2,……,n, j 0

such that where

 n   n1  ......  1   0  0 ,

 n  0 , then P(z) has all its zeros in

||Issn 2250-3005(online)||

||January || 2013

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