Align equations

Question

I have to put three equations. I am using the following code:

\begin{gather}
m_{1,1}^i = \sum (x - \bar{x}^i) (y - \bar{y}^i)\text{,} \\
m_{2,0}^i = \sum (x - \bar{x}^i)^2 \text{ and} \\
m_{0,2}^i = \sum (y - \bar{y}^i)^2 \text{ } \forall  \text{ } n(x,y) \in G_i
\end{gather}

What I am getting:

What I need:

Question: How can I align the left starting of all the three equations?

Answer 1

align can be found in the amsmath guide. Note that the ampersands define what to align. In this situation, put & before the "=" of each equation.

\begin{align}
 m_{1,1}^i &= \sum (x - \bar{x}^i) (y - \bar{y}^i)\text{,} \\
 m_{2,0}^i &= \sum (x - \bar{x}^i)^2 \text{ and} \\
 m_{0,2}^i &= \sum (y - \bar{y}^i)^2 \text{ } \forall  \text{ } n(x,y) \in G_i
\end{align}