# How to break lines in a long equation in the following way? Just what I titled out, how to realize the following results?

• It seems that it couldn't be completed by "split" or "align" environments. – M. Logic Aug 7 '17 at 5:09
• – M. Logic Aug 7 '17 at 5:11

I suggest you load the amsmath package and use its bmatrix ("bracketed matrix") environment. \documentclass{article}
\usepackage{amsmath,bm,newtxtext,newtxmath}

\begin{document}
$(\forall \bm{p}) \begin{bmatrix} (\forall x) (\varphi(x,\bm{p}) \leftrightarrow \cdots ) \to \\ \bigl((\varphi(0,\bm{p}) \wedge (\varphi(x,\bm{p}) \to \varphi(x+1,\bm{p}))) \to \cdots \bigr) \end{bmatrix}$
\end{document}

• Uhhh! You're 20 sec faster, (+1)-; – AboAmmar Aug 7 '17 at 5:59

You can use bmatrix from amsmath package for this. If you need also italic bold math, load the bm package and use \bm{..} instead of \mathbf{..}.

\documentclass[a4paper,10pt]{article}
\usepackage{amsmath}
\begin{document}

$(\forall \mathbf{p}) \begin{bmatrix} (\forall x) ( \varphi(x,\mathbf{p}) \leftrightarrow \neg\psi(x,\mathbf{p}))\rightarrow\\ \bigl((\varphi(0,\mathbf{p}) \wedge (\varphi(x,\mathbf{p})\to\varphi(x+1,\mathbf{p})))\to(\forall x)\varphi(x,\mathbf{p})\bigr) \end{bmatrix}$

\end{document} • but these p are vertical, haha – M. Logic Aug 7 '17 at 6:32

In my opinion, gathered is the best choice. I also implemented new commands, because in this context the arrows should be binary operation symbols.

\documentclass{article}
\usepackage{newtxtext,newtxmath}
\usepackage{amsmath,bm}

\newcommand{\vp}{\bm{p}}
\newcommand{\liff}{\mathbin{\leftrightarrow}}
\newcommand{\limpl}{\mathbin{\rightarrow}}

\begin{document}

$(\forall \vp) \left[ \begin{gathered} (\forall x) (\varphi(x,\vp) \liff \dotsb ) \limpl {}\\ \bigl((\varphi(0,\vp) \land (\varphi(x,\vp) \limpl \varphi(x+1,\vp))) \to \dotsb \bigr) \end{gathered} \right]$

\end{document} 