\documentclass[llpt]{article}
 \usepackage[utf8]{inputenc}
  \usepackage[greek,english]{babe]}
  %\usepackage{mathptmx}
  \usepackage[scaled]{helvet}
  \usepackage{alphabeta}
  \usepackage{fancyhdr}
   \begin{document}
    \section{eisagogi}

Hello this is English text

auto einai mia paragrafos

auto einai mia deuteri paragrafos


\[x^2+y^2-\alpha=4\tau + 5\alpha  \]
\end{document}
%telos twn paketwn


