# How to arrange an align and/or arrangement of equations when their lengths are different?

I have a set of equations with greater length difference. Two first equations are short and two last equations are very long.

Question. How to arrange an align and an arrangement of equations for more readability?

\documentclass[12pt]{article}
\usepackage{amsmath}

\begin{document}
\begin{eqnarray}\label{EQ4}
\alpha_{0} &=&1-\frac{t}{h},  \\ \nonumber
%
\alpha _{1} &=&\frac{t}{h},  \\ \nonumber
%
\alpha _{2} &=&\frac{1}{2520} \frac{756h^{3} +135h}{h^{3}}
-\frac{1}{7560} \frac{(1869h^{4} +1950h^{2} +70)t}{h^{3} }
+\frac{1}{270} \frac{\left(54h^{3} +15h\right)\left(\frac{5}{2}
t^{2} -\frac{3}{2} \right)}{h^{3} } \\ \nonumber &-&
\frac{1}{6930} \frac{\left(715h^{2} +42\right)\left(\frac{7}{2}
t^{3} -\frac{5}{2} x+\frac{5}{2} x_{n} \right)}{h^{3} }
-\frac{1}{63} \frac{\frac{63}{8} t^{4} -\frac{35}{4} t^{2}
+\frac{15}{8} }{h^{2} } -\frac{2}{185} \frac{\frac{99}{8} t^{5}
-\frac{63}{4} t^{3} +\frac{35}{8} x-\frac{35}{8} x_{n} }{h^{3} },
\\ \nonumber
%
\alpha _{3} &=&-\frac{1}{4h^{} } -\frac{1}{1260}
\frac{\left(651h^{4} -900h^{2} -70\right)t}{h^{3} } -\frac{7}{27}
\frac{\frac{5}{2} t^{2} -\frac{3}{2} }{h^{2} } +\frac{2}{1155}
\frac{\left(165h^{2} +21\right)\left(\frac{7}{2} t^{3}
-\frac{5}{2} t\right)}{h^{3} } \\ \nonumber &-& \frac{2}{27}
\frac{\frac{63}{8} t^{4} -\frac{35}{4} t^{2} +\frac{15}{8} }{h^{2}
} +\frac{4}{495} \frac{\frac{99}{8} t^{5} -\frac{63}{4} t^{3}
+\frac{35}{8} t}{h^{3} },  \\ \nonumber

\end{eqnarray}
\end{document}

• Do you have access to a computer algebra system? (How did you get these results?) If I am not mistaken, the constant term in \alpha_2 just adds up to 3/5 and so on. The best thing you can do for the optics is IMHO to simplify the expressions in the computer algebra system and then use align rather than eqnarray. (I personally would also use subequations for the coefficients.) – user121799 Apr 21 '18 at 0:59

Here is a possibility, with align and the \medsize command from nccmath:

\documentclass[12pt]{article}
\usepackage[a4paper, showframe]{geometry}
\usepackage{mathtools, nccmath}

\begin{document}

\begin{align}\label{EQ4}
\alpha_{0} &= 1-\frac{t}{h}, \\ \nonumber
%
\alpha _{1} &= \frac{t}{h}, \\ \nonumber
%
\alpha _{2} &=\medmath{\begin{aligned}[t] \frac{1}{2520} \frac{756h^{3} +135h}{h^{3}}
-\frac{1}{7560} \frac{(1869h^{4} +1950h^{2} +70)t}{h^{3} }
+\frac{1}{270} \frac{\left(54h^{3} +15h\right)\biggl({5}{2}
t^{2} -\cfrac{3}{2} \biggr)}{h^{3} } \\-
\frac{1}{6930} \frac{\left(715h^{2} +42\right)\left(\dfrac{7}{2}
t^{3} -\dfrac{5}{2} x+\dfrac{5}{2} x_{n} \right)}{h^{3} } %\\ \nonumber
-\frac{1}{63} \frac{\dfrac{63}{8} t^{4} -\dfrac{35}{4} t^{2}
+\dfrac{15}{8} }{h^{2}}\\ -\frac{2}{185} \frac{\dfrac{99}{8} t^{5}
-\dfrac{63}{4} t^{3} +\dfrac{35}{8} x-\dfrac{35}{8} x_{n} }{h^{3}},
\end{aligned}}\nonumber\\[1.5ex]
%
\alpha _{3} &=\medmath{\begin{aligned}[t] -\frac{1}{4h^{} } -\frac{1}{1260}
\frac{\left(651h^{4} -900h^{2} -70\right)t}{h^{3} } -\frac{7}{27}
\frac{\dfrac{5}{2} t^{2} -\dfrac{3}{2} }{h^{2} } +\frac{2}{1155}
\frac{\left(165h^{2} +21\right)\left(\dfrac{7}{2} t^{3}
-\dfrac{5}{2} t\right)}{h^{3}} \\- \frac{2}{27}
\frac{\dfrac{63}{8} t^{4} -\dfrac{35}{4} t^{2} +\dfrac{15}{8}}{h^{2}
} +\frac{4}{495} \frac{\dfrac{99}{8} t^{5} -\dfrac{63}{4} t^{3}
+\dfrac{35}{8} t}{h^{3}} ,
\end{aligned}} \nonumber
\end{align}

\end{document}


alternatively you can use the multlined math environment and \mfrac instead of the \dfrac:

\documentclass[12pt]{article}
\usepackage[a4paper]{geometry}
\usepackage{mathtools, nccmath}

%---------------- show page layout. don't use in a real document!
\usepackage{showframe}
\renewcommand\ShowFrameLinethickness{0.15pt}
\renewcommand*\ShowFrameColor{\color{red}}
%---------------------------------------------------------------%

\begin{document}

\begin{align}\label{EQ4}
\alpha_{0}  & = 1-\frac{t}{h},          \\
%
\alpha_{1}  & = \frac{t}{h},    \notag  \\
%
\alpha_{2}  & = \medmath{\begin{multlined}[t]
\frac{1}{2520}\frac{756h^{3} + 135h}{h^{3}}
-\frac{1}{7560}\frac{(1869h^{4} + 1950h^{2} + 70)t}{h^{3}}  \\
+\frac{1}{270}\frac{\left(54h^{3} + 15h\right)
\left({5}{2}t^{2} - \mfrac{3}{2} \right)}{h^{3} }
- \frac{1}{6930}\frac{\left(715h^{2} + 42\right)
\left(\mfrac{7}{2}t^{3} - \mfrac{5}{2} x + \mfrac{5}{2} x_{n} \right)}{h^{3} }                                    \\
-\frac{1}{63} \frac{\mfrac{63}{8} t^{4} - \mfrac{35}{4} t^{2}
+ \mfrac{15}{8} }{h^{2}}
- \frac{2}{185} \frac{\mfrac{99}{8} t^{5}
-\mfrac{63}{4} t^{3} +\mfrac{35}{8} x-\mfrac{35}{8} x_{n} }{h^{3}},
\end{multlined}}        \notag  \\[2ex]
%
\alpha_{3}  & = \medmath{\begin{multlined}[t]
-\frac{1}{4h^{} } -\frac{1}{1260}\frac{\left(651h^{4} - 900h^{2} -70\right)t}{h^{3} } - \frac{7}{27}\frac{\mfrac{5}{2} t^{2}  -\mfrac{3}{2} }{h^{2} } \\
+ \frac{2}{1155}\frac{\left(165h^{2} + 21\right)\left(\mfrac{7}{2} t^{3}
-\mfrac{5}{2} t\right)}{h^{3}}
- \frac{2}{27}\frac{\mfrac{63}{8} t^{4} - \mfrac{35}{4} t^{2} + \mfrac{15}{8}}{h^{2}} + \frac{4}{495} \frac{\mfrac{99}{8} t^{5} -\mfrac{63}{4} t^{3} +\mfrac{35}{8} t}{h^{3}} ,
\end{multlined}} \notag
\end{align}
\end{document}