Second Hankel determinant for a subclass of analytic bi-univalent functions defined by subordination

Abstract

In this work with a different technique we obtain upper bounds of the functional $\left|a_2a_4-a_3^2\right|$ for functions belonging to a comprehensive subclass of analytic bi-univalent functions, which is defined by subordinations in the open unit disk. Moreover, our results extend and improve some of the previously known ones.