\documentclass[12pt]{article}
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\author{ΓΕΩΡΓΙΑ ΜΟΥΔΙΩΤΗ}
\title{1η εργαστηριακη ασκηση}
\date{15/6/2021}
\begin{document}
\maketitle
\section{mia anafora}
ayth einai mia syntoh anafora
\begin{equation}
\begin{array}{r}
f(n)=\sum_{m=2}^{n}\left[\left(\sum_{k=1}^{m-1}(m/k)/[m/k]\right\rfloor\right)^{-1}]\\
\end{array}
\end{equation}
\begin{equation}
A=\left(\begin{array}{cccc}
a_{11}&a_{12}&\cdots &a_{1n}\\
a_{21}&a_{22}&\cdots &a_{2n}\\
\vdots &\vdots &\ddots &\vdots\\
a_{m1}&a_{m2}&\cdots &a_{mn}
\end{array}\right)\\
\end{equation}
\begin{equation}
\left\{\begin{array}{l}
a=f(z)\\
b=f\left(z^{2}\right)\\
c=f\left(z^{3}\right)
\end{array}\right\}
\end{equation}
\begin{equation}
p_{1}(n)=\lim_{m\to\infty}\sum_{ν=0}^{\infty}(1-cos^{2m}(ν!^{n}π/n))
\end{equation}
\begin{equation}
\prod_{j>0}(\sum_{k>=0}a_{jk}z^{k})=\sum_{n>=0}z^n(\sum_{k_{0},k_{1}\cdots>=0\\k_{0}+k_{1}\cdots =n}a_{0k_{0}}a_{1}k_{1}\cdots)
\end{equation}
\end{document}
