\documentclass{article}
\include{macros}
\renewcommand{\Q}{\mathbf{Q}}
\begin{document}
$$y^2 = x^3 + ax + b$$
$$\mbox{\rm disc}(E) = -16(4a^3 + 27b^2) \neq 0$$
$$E(\Q) = \{(x,y)\in\Q\times\Q : y^2 = x^3 + ax + b\}\cup\{\infty\}$$
$$\Gal(\Qbar/\Q)$$
\end{document}