\documentclass{article}
\usepackage{amsmath}
\begin{document}

This is an equation environment in which there is an array environment.  The equation below
is just a simple matrix equation without delimeters.  The three types of alignment are
tested.  
\begin{equation*}
w =  
\begin{array}{lcr}
x+y & y+2c & z * x^2 \\
x & y & z \\
x & y & z \\
x & y & z 
\end{array}
\end{equation*}

This is an equation environment in which there is an array environment.  The equation below
is just a simple matrix equation.  The three types of alignment are
tested.  
\begin{equation}
w = \left( 
\begin{array}{lcr}
x+y & y+2c & z * x^2 \\
x & y & z \\
x & y & z \\
x & y & z 
\end{array}
\right)
\end{equation}
\end{document}

