To align equation

Question

How to align the equation below with number in center of equation? And I need that the equations have same length.

\begin{equation}
\begin{aligned}
VAR(X)&=\frac{1}{12m}\sum_{u \in \Omega}\left( a_{u1}^2 +a_{u2}^2 + a_{u3}^2 + a_{u1}a_{u2} + a_{u1}a_{u3} + a_{u2}a_{u3}\right) - \left[ \frac{1}{m}\sum_{u \in \Omega} \frac{a_{u1} + a_{u2} + a_{u3}}{3} \right]^2\\
VAR(Y)&=\frac{1}{12m}\sum_{u \in \Omega}\left( b_{u1}^2 +b_{u2}^2 + b_{u3}^2 + b_{u1}b_{u2} + b_{u1}b_{u3} + b_{u2}b_{u3}\right) - \left[ \frac{1}{m}\sum_{u \in \Omega} \frac{b_{u1} + b_{u2} + b_{u3}}{3} \right]^2
\label{eq:variancia_amostral_triangulo_x_y}
\end{aligned}
\end{equation}

Wrong mode.

Answer 1

This does the trick.... and makes VAR look less like V times A times R.

    \documentclass{article}

    \usepackage{amsmath}

    \begin{document}
    \begin{equation}
    \begin{aligned}
    \mathrm{VAR}(X)&=\frac{1}{12m}\sum_{u \in \Omega}\left( a_{u1}^2 +a_{u2}^2 + a_{u3}^2 + a_{u1}a_{u2} + a_{u1}a_{u3} + a_{u2}a_{u3}\right) \\
     & \qquad - \left[ \frac{1}{m}\sum_{u \in \Omega} \frac{a_{u1} + a_{u2} + a_{u3}}{3} \right]^2\\
    \mathrm{VAR}(Y)&=\frac{1}{12m}\sum_{u \in \Omega}\left( b_{u1}^2 +b_{u2}^2 + b_{u3}^2 + b_{u1}b_{u2} + b_{u1}b_{u3} + b_{u2}b_{u3}\right) 
    \\
    &\qquad - \left[ \frac{1}{m}\sum_{u \in \Omega} \frac{b_{u1} + b_{u2} + b_{u3}}{3} \right]^2
    \end{aligned}
     \label{eq:variancia_amostral_triangulo_x_y}
   \end{equation}

    \end{document}