\documentclass{article}
\usepackage{amsmath}
\usepackage{xepersian}

\begin{document}
\begin{align*}
max \qquad &\hat{R}_S(\mathbf{x})= R_S(\mathbf{x})+\delta(\mathbf{x})\\
&\qquad \qquad \qquad \qquad \qquad \qquad \qquad \qquad \qquad \qquad  \text{که}\\
&\delta(\mathbf{x})=\left\lbrace\begin{array}{lr}
[0,0] & \mathbf{x}\in S\quad \text{اگر}\\
-R_S(\mathbf{x}) +[-M,-M] & \mathbf{x}\notin S \quad \text{اگر}
\end{array}
\end{align*}
\end{document}