مثال کمینه زیر را ببینید:
\documentclass{book}
\usepackage{geometry}
\usepackage{amsmath}
\usepackage{xepersian}
\settextfont{Yas}
\renewcommand{\baselinestretch}{2}
\begin{document}
با استفاده از داده‌های موجود در جدول\ref{بازده-1} و \ref{واریانس1} به صورت زیر فرمول‌بندی می‌نماییم:
\begin{align*}
\max f_{1}(x) &= -0.1914x_{1}+0.2497x_{2}-0.0191x_{3}-0.0032x_{4}+0.0128x_{5} \\
& +0.0893x_{6}-0.0282x_{7}-0.0592x_{8}-0.1928x_{9}+0.0306x_{10}+0.0372x_{11} \\
& -0.074x_{12}+0.0386x_{13}+0.0675x_{14}\\
\min & f_{2}(x)=0.0956x_{1}x_{1}+0.0691x_{2}x_{2}+0.0128x_{3}x_{3}+0.0073x_{4}x_{4}+.0107x_{5}x_{5}\\
& +0.0153x_{6}x_{6}+.0510x_{7}x_{7}+0.0118x_{8}x_{8}+0.0355x_{9}x_{9}+0.0176x_{10}x_{10}+0.0103x_{11}x_{11}\\
&+0.0138x_{12}x_{12}+0.0068x_{13}x_{13}+0.0071x_{14}x_{14}+0.0986x_{1}x_{2}+.0396x_{1}x_{3}\\
&-0.028x_{1}x_{4}-0.0378x_{1}x_{5}+0.008x_{1}x_{6}+0.0956x_{1}x_{7}-0.0284x_{1}x_{8}\\
&+0.017x_{1}x_{9}-0.0306x_{1}x_{10}-0.0372x_{1}x_{11}-0.0112x_{1}x_{12}-0.049x_{1}x_{13}
\end{align*}
\begin{align*}
\max f_{1}(x) &= -0.1914x_{1}+0.2497x_{2}-0.0191x_{3}-0.0032x_{4}+0.0128x_{5} \\
& +0.0893x_{6}-0.0282x_{7}-0.0592x_{8}-0.1928x_{9}+0.0306x_{10}+0.0372x_{11} \\
& -0.074x_{12}+0.0386x_{13}+0.0675x_{14}\\
\min & f_{2}(x)=0.0956x_{1}x_{1}+0.0691x_{2}x_{2}+0.0128x_{3}x_{3}+0.0073x_{4}x_{4}+.0107x_{5}x_{5}\\
& +0.0153x_{6}x_{6}+.0510x_{7}x_{7}+0.0118x_{8}x_{8}+0.0355x_{9}x_{9}+0.0176x_{10}x_{10}+0.0103x_{11}x_{11}\\
&+0.0138x_{12}x_{12}+0.0068x_{13}x_{13}+0.0071x_{14}x_{14}+0.0986x_{1}x_{2}+.0396x_{1}x_{3}\\
&-0.028x_{1}x_{4}-0.0378x_{1}x_{5}+0.008x_{1}x_{6}+0.0956x_{1}x_{7}-0.0284x_{1}x_{8}\\
&+0.017x_{1}x_{9}-0.0306x_{1}x_{10}-0.0372x_{1}x_{11}-0.0112x_{1}x_{12}-0.049x_{1}x_{13} \\
\max f_{1}(x) &= -0.1914x_{1}+0.2497x_{2}-0.0191x_{3}-0.0032x_{4}+0.0128x_{5} \\
& +0.0893x_{6}-0.0282x_{7}-0.0592x_{8}-0.1928x_{9}+0.0306x_{10}+0.0372x_{11} \\
& -0.074x_{12}+0.0386x_{13}+0.0675x_{14}\\
\min & f_{2}(x)=0.0956x_{1}x_{1}+0.0691x_{2}x_{2}+0.0128x_{3}x_{3}+0.0073x_{4}x_{4}+.0107x_{5}x_{5}\\
& +0.0153x_{6}x_{6}+.0510x_{7}x_{7}+0.0118x_{8}x_{8}+0.0355x_{9}x_{9}+0.0176x_{10}x_{10}+0.0103x_{11}x_{11}\\
&+0.0138x_{12}x_{12}+0.0068x_{13}x_{13}+0.0071x_{14}x_{14}+0.0986x_{1}x_{2}+.0396x_{1}x_{3}\\
&-0.028x_{1}x_{4}-0.0378x_{1}x_{5}+0.008x_{1}x_{6}+0.0956x_{1}x_{7}-0.0284x_{1}x_{8}\\
&+0.017x_{1}x_{9}-0.0306x_{1}x_{10}-0.0372x_{1}x_{11}-0.0112x_{1}x_{12}-0.049x_{1}x_{13}
\end{align*}
\end{document}
اگر این فایل را اجرا کنید خواهید دید که فرمول بزرگ دوم که در یک محیط align نوشته شده است، به صفحه بعد می رود و صفحه اول مشکل شما را دارد. البته این مشکل از لاتک نیست. لاتک در کلاس book سعی می کند که صفحه را پر کند. به همین دلیل فاصله ایجاد شده است.
برای این کار یکی از راه حل ها این است که در محیط align دوم در یکی از خطوطی که مناسب می‌دانید از فرمان \displaybreak استفاده کنید.
مثلا کد زیر را ببینید:
\documentclass{book}
\usepackage{geometry}
\usepackage{amsmath}
\usepackage{xepersian}
\settextfont{Yas}
\renewcommand{\baselinestretch}{2}
\begin{document}
با استفاده از داده‌های موجود در جدول\ref{بازده-1} و \ref{واریانس1} به صورت زیر فرمول‌بندی می‌نماییم:
\begin{align*}
\max f_{1}(x) &= -0.1914x_{1}+0.2497x_{2}-0.0191x_{3}-0.0032x_{4}+0.0128x_{5} \\
& +0.0893x_{6}-0.0282x_{7}-0.0592x_{8}-0.1928x_{9}+0.0306x_{10}+0.0372x_{11} \\
& -0.074x_{12}+0.0386x_{13}+0.0675x_{14}\\
\min & f_{2}(x)=0.0956x_{1}x_{1}+0.0691x_{2}x_{2}+0.0128x_{3}x_{3}+0.0073x_{4}x_{4}+.0107x_{5}x_{5}\\
& +0.0153x_{6}x_{6}+.0510x_{7}x_{7}+0.0118x_{8}x_{8}+0.0355x_{9}x_{9}+0.0176x_{10}x_{10}+0.0103x_{11}x_{11}\\
&+0.0138x_{12}x_{12}+0.0068x_{13}x_{13}+0.0071x_{14}x_{14}+0.0986x_{1}x_{2}+.0396x_{1}x_{3}\\
&-0.028x_{1}x_{4}-0.0378x_{1}x_{5}+0.008x_{1}x_{6}+0.0956x_{1}x_{7}-0.0284x_{1}x_{8}\\
&+0.017x_{1}x_{9}-0.0306x_{1}x_{10}-0.0372x_{1}x_{11}-0.0112x_{1}x_{12}-0.049x_{1}x_{13}
\end{align*}
\begin{align*}
\max f_{1}(x) &= -0.1914x_{1}+0.2497x_{2}-0.0191x_{3}-0.0032x_{4}+0.0128x_{5} \\
& +0.0893x_{6}-0.0282x_{7}-0.0592x_{8}-0.1928x_{9}+0.0306x_{10}+0.0372x_{11} \\
& -0.074x_{12}+0.0386x_{13}+0.0675x_{14}\\
\min & f_{2}(x)=0.0956x_{1}x_{1}+0.0691x_{2}x_{2}+0.0128x_{3}x_{3}+0.0073x_{4}x_{4}+.0107x_{5}x_{5}\\
& +0.0153x_{6}x_{6}+.0510x_{7}x_{7}+0.0118x_{8}x_{8}+0.0355x_{9}x_{9}+0.0176x_{10}x_{10}+0.0103x_{11}x_{11}\\
&+0.0138x_{12}x_{12}+0.0068x_{13}x_{13}+0.0071x_{14}x_{14}+0.0986x_{1}x_{2}+.0396x_{1}x_{3}\\
&-0.028x_{1}x_{4}-0.0378x_{1}x_{5}+0.008x_{1}x_{6}+0.0956x_{1}x_{7}-0.0284x_{1}x_{8}\\
&+0.017x_{1}x_{9}-0.0306x_{1}x_{10}-0.0372x_{1}x_{11}-0.0112x_{1}x_{12}-0.049x_{1}x_{13} \\ \displaybreak
\max f_{1}(x) &= -0.1914x_{1}+0.2497x_{2}-0.0191x_{3}-0.0032x_{4}+0.0128x_{5} \\
& +0.0893x_{6}-0.0282x_{7}-0.0592x_{8}-0.1928x_{9}+0.0306x_{10}+0.0372x_{11} \\
& -0.074x_{12}+0.0386x_{13}+0.0675x_{14}\\
\min & f_{2}(x)=0.0956x_{1}x_{1}+0.0691x_{2}x_{2}+0.0128x_{3}x_{3}+0.0073x_{4}x_{4}+.0107x_{5}x_{5}\\
& +0.0153x_{6}x_{6}+.0510x_{7}x_{7}+0.0118x_{8}x_{8}+0.0355x_{9}x_{9}+0.0176x_{10}x_{10}+0.0103x_{11}x_{11}\\
&+0.0138x_{12}x_{12}+0.0068x_{13}x_{13}+0.0071x_{14}x_{14}+0.0986x_{1}x_{2}+.0396x_{1}x_{3}\\
&-0.028x_{1}x_{4}-0.0378x_{1}x_{5}+0.008x_{1}x_{6}+0.0956x_{1}x_{7}-0.0284x_{1}x_{8}\\
&+0.017x_{1}x_{9}-0.0306x_{1}x_{10}-0.0372x_{1}x_{11}-0.0112x_{1}x_{12}-0.049x_{1}x_{13}
\end{align*}
\end{document}
روش بعد استفاده از \allowdisplaybreaks در دیباچه است که لاتک خود تصمیم بگیرد کجا فرمول را بشکند.
