\begin{eqnarray}
Ly = \lambda y
\end{eqnarray}

\begin{gather*}
\begin{split}
b=1\\ 
a=b
\end{split}\\[6pt]
\end{gather*}

\begin{gather*}
\begin{split} 
a &= m\   &= k
\end{split}\\[6pt]
\begin{align} 
b &= i ,\c &= j
\end{align}
\end{gather*}