% Equation exercise from ../latex.md, using the recommended align environment.
% The integral ends at x and the sum starts at i=0, correcting the old screenshot.
% Build instructions: latex-for-beginners-common.tex.
\documentclass[a4paper,12pt]{article}
\input{latex-for-beginners-common.tex}
\usepackage{amsmath}
\begin{document}
\begin{align}
  e &= mc^2 \\
  \pi &= \frac{c}{d} \\
  \frac{d}{dx} e^x &= e^x \\
  \frac{d}{dx} \int_0^x f(s)\,ds &= f(x) \\
  f(x) &= \sum_{i=0}^{\infty} \frac{f^{(i)}(0)}{i!} x^i \\
  x &= \sqrt{\frac{x_i}{z} y}
\end{align}
\end{document}