关于某些具有负系数的解析函数

On Some Classes of Analytic Functions with Negative Coefficient

Let A denote the class of funetions f(z) defined by f(z)=z-sum from n=2 to ∞a_nz^n (a_n>0) (1) which are analytic in the unit disk U= {z:|z|<1}. A function f(z)∈A is said to be in the class S (x,β,γ), if and only if |(f′(z)-1)/(af′(z)+1-(1+α)β)|<γ(2) for 0<x<1, 0<β<1, and 0<<1.