ON SUBCLASSES OF UNIVALENT FUNCTIONS WITH NEGATIVE COEFFICIENTS

  • Owa, Shigeyoshi (Kinki University, Japan) ;
  • Aouf, M.K. (Faculty of Science University of Mansoura, Egypt, Faculty of Science University of Qatar)
  • Published : 1988.06.25

Abstract

The subclasses S*($\alpha,\beta,\mu$) and C*($\alpha,\beta,\mu$) ($0\leqq\alpha<1,\;0<\beta\leqq1$ and $0\leqq\mu\leqq1$) of T the class of analytic and univalent functions of the form $$f(z)=z-\sum\limit^{\infty}_{n=2}\mid a_n\mid z^n$$ have been considered. Sharp results concerning coefficients, distortion of functions belonging to S*($\alpha,\beta,\mu$) and C*($\alpha,\beta,\mu$) are determined along with a representation formula for the functions in S*($\alpha,\beta,\mu$). Furthermore, it is shown that the classes S*($\alpha,\beta,\mu$) and C*($\alpha,\beta,\mu$) are closed under arithmetic mean and convex linear combinations. Also in this paper, we find extreme points and support points for these classes.

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