LaTeX用equation* + aligned报错

问题遇到的现象和发生背景

写LaTeX时对齐公式，结果报错missing } inserted.

\begin{equation*}
    \begin{aligned}
    {
        {\text{原式} &= $\dfrac{\(x\-y\)\(x\+y\)}{a\(x\+y\)}$\\} 
    {&= $\dfrac{x-y}{a}$\\}
    }
    
    \end{aligned}
\end{equation*}

急，求快速回答！

\begin{equation*}
\begin{aligned}
\text{原式} & = \frac{(x-y)(x+y)}{a(x+y)} \\
& = \frac{x-y}{a}
\end{aligned}
\end{equation*}