Re: scrivere un’equazione

`\documentclass{book}
\usepackage{amsmath}
\begin{document}
\begin{align}\label{eq:FFD}
F(\mathbf{x}, t+\Delta t) & = F(\mathbf{x}, t) + \frac{\partial F(\mathbf{x},t)}{\partial t}\Delta t\\
& = F(\mathbf{x}, t) + G(\mathbf{x},t)|\mathbf{\nabla}F(\mathbf{x}, t)\Delta t
\end{align}
\end{document}`
L’ambiente align non va dentro l’ambiente equation.

Ciao,
ansys.