a1 School of Mathematical Sciences, University of Khartoum, P0 Box 321, Khartoum, Sudan.
Abstract
Let
be analytic in the unit disc U(|z| <1) and let F(z) = (l-λ)f (Z) + λ(f(z)*h(z)) where
with cn 's are known and are nonnegative, λ ≥ 0 In the present paper, using convolution methods we investigate the mapping properties of F(z) when f(z) belongs respectively to several subclasses of analytic functions with negative coefficients.
(Received October 10 1983)