formattingmatrices
\documentclass{amsart}
\usepackage{amsmath}%
\usepackage{amsfonts}%
\usepackage{amssymb}%
\begin{document}
\begin{align*}
\tau_A
\begin{pmatrix}
x \\
y
\end{pmatrix}
=
\begin{pmatrix}
\frac{4+5x+6y}{1+2x+3y} \\
\frac{7+8x+8y}{1+2x+3y}
\end{pmatrix}
\end{align*}
\end{document}
This code has the following output:
Is there anyway to separate the elements in the right hand column vector in order to make the fractions clearer to distinguish?
\documentclass{article}
\usepackage{amsmath}
\begin{document}
\begin{gather*}
\mbox{\scriptsize%
$A = \begin{bmatrix} a & b & c \\ d & e & f \\ g & h & i \end{bmatrix}$}\\
A = \begin{bmatrix} a & b & c \\ d & e & f \\ g & h & i \end{bmatrix}
\end{gather*}
\end{document}
To illustrate @JohnKormylo's comment, you would need to put it in place of the \\ you have already. Changing your MWE (for a gap of 10pt):
\documentclass[10pt,a4paper]{article}
\usepackage[latin1]{inputenc}
\usepackage{amsmath}
\usepackage{amsfonts}
\usepackage{amssymb}
\begin{document}
\begin{align*}
Var(u) &= E(uu') = \\
&= E
\begin{bmatrix}
u_1 u_1' & u_1 u_2' & \cdots & u_1 u_M' \\
u_2 u_1' & u_2 u_2' & \cdots & u_2 u_M' \\
\vdots & & \ddots & \vdots \\
u_M u_1' & u_M u_2' & \cdots & u_M u_M '
\end{bmatrix}
=
\begin{bmatrix}
\sigma_{11} I & \sigma_{12} I & \cdots & \sigma_{1M} I \\
\sigma_{12} I & \sigma_{22} I & \cdots & \sigma_{2M} I \\
\vdots & & \ddots & \vdots\\
\sigma_{1n} I & \sigma_{2M} I & \cdots & \sigma_{MM} I
\end{bmatrix} \\[10pt] %%%%%%%%%%%%%%%%% Change this for different spacing
&=
\begin{pmatrix}
\sigma_{11} & \sigma_{12} & \cdots & \sigma_{1M} \\
\sigma_{12} & \sigma_{22} & \cdots & \sigma_{2M} \\
\vdots & & \ddots & \vdots \\
\sigma_{1M} & \sigma_{2M} & \cdots & \sigma_{MM}
\end{pmatrix}_{\otimes I_T}
\end{align*}
\end{document}\documentclass[]{article}
\begin{document}
\title{Title}
\author{Author}
\date{Today}
\maketitle
Content
\end{document}
Best Answer
You can increase specify extra an space to go between the rows after
\\. You can also make the fractions bigger with\displaystyleif necessary.Here I used
1cmto show the effect clearly; a space this big is probably excessive.