\documentclass[aps,twocolumn]{revtex4}
\usepackage{epsfig}
\usepackage{amsmath}
\usepackage{epsfig}
\renewcommand{\baselinestretch}{1.45}
\begin{document}
\begin{multline}
2F_1(a,b,c,y){=}\frac{\Gamma(c)\Gamma(c-a-b)}{\Gamma(c-a)\Gamma(c-
b)}~_2F_1(a,b,a+b-c+1,1-y)+\\
\frac{\Gamma(c)\Gamma(a+b-c)}{\Gamma(a)\Gamma(b)}(1-y)^{c-a-
b}~_2F_1(c-a,c-b,c-a-b+1,1-y)
\end{multline}
\end{document}
In two column document class,Equation number is not coming on the line where equation ends, instead it comes in next line, please help ??