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On the generalized derivative of a polynomial with restricted zeros

  • F. A. Bhat,
  • H. A. Dar

摘要

Let \(p(z)=c\prod _{j=1}^{n}(z-z_j)\) p ( z ) = c j = 1 n ( z - z j ) with \(~c\ne 0\) c 0 be a polynomial of degree n and \(p^\gamma (z)\) p γ ( z ) be its generalized derivative, where \(0\ne \gamma =(\gamma _1,\gamma _2,\ldots ,\gamma _n)\) 0 γ = ( γ 1 , γ 2 , , γ n ) is an n-tuples of non-negative real numbers in the Euclidean space \(\mathbb {R}^n\) R n . In this paper, we consider a class of polynomials having all zeros in \(|z|\le \rho , ~\rho \le 1\) | z | ρ , ρ 1 and investigate the dependence of \(\max _{|z|=1}\bigg |zp^\gamma (z)+\frac{\Lambda \beta }{1+\rho }p(z)\bigg |\) max | z | = 1 | z p γ ( z ) + Λ β 1 + ρ p ( z ) | on \(\max _{|z|=1} |p(z)|,\) max | z | = 1 | p ( z ) | , where \(\beta \) β is any complex number with \(|\beta |\le 1\) | β | 1 and \(\Lambda =\sum _{j=1}^{n}\gamma _j.\) Λ = j = 1 n γ j . Our results not only generalize several established polynomial inequalities, but also enable the derivation of a variety of interesting outcomes through a consistent approach. In addition to it, we also present some generalizations of Turán’s inequality.