请问latex中公式如何等号对齐啊?我的公式代码如下：\begin{eqnarray}\label{eqn3_2}\begin{array}{ll}\underbrace {\left[ {\begin{array}{*{20}{c}}{y(1)}&{y(2)}& \cdots &{y(L)}\end{array}} \right]}_Y = \Theta \underbrace {\le