A test of Equation Numbering

Equation: \[\begin{equation} E = mc^2 \end{equation}\] Equation*: \[\begin{equation*} E = mc^2 \end{equation*}\]

Brackets: \[E = mc^2\] Brackets tagged: \[E = mc^2\tag{x}\]

\[\begin{equation} \begin{split} a& =b+c-d\\ & \quad +e-f\\ & =g+h\\ & =i \end{split} \end{equation}\]

Multline:

\[\begin{multline} a+b+c+d+e+f+g\\ M+N+O+P+Q\\ R+S+T\\ u+v+w+x+y+z \end{multline}\]

Multline*:

\[\begin{multline*} a+b+c+d+e+f+g\\ M+N+O+P+Q\\ R+S+T\\ u+v+w+x+y+z \end{multline*}\]

Gather:

\[\begin{gather} a_1=b_1+c_1\\ a_2=b_2+c_2-d_2+e_2 \end{gather}\]

Gather*:

\[\begin{gather*} a_1=b_1+c_1\\ a_2=b_2+c_2-d_2+e_2 \end{gather*}\]

Align:

\[\begin{align} a_1& =b_1+c_1\\ a_2& =b_2+c_2-d_2+e_2 \end{align}\]

Align*:

\[\begin{align*} a_1& =b_1+c_1\\ a_2& =b_2+c_2-d_2+e_2 \end{align*}\]

Align:

\[\begin{align} a_{11}& =b_{11}& a_{12}& =b_{12}\\ a_{21}& =b_{21}& a_{22}& =b_{22}+c_{22} \end{align}\]

Align with and :

\[\begin{align} a_{11}& =b_{11}& a_{12}& =b_{12}\notag\\ a_{21}& =b_{21}& a_{22}& =b_{22}+c_{22} \tag{y} \end{align}\]

Align* with :

\[\begin{align*} a_1& =b_1+c_1\tag{z}\\ a_2& =b_2+c_2-d_2+e_2 \end{align*}\]