Find the multiple regression equation for the data given below. $$\begin{array}{r|rrrrr} x_1 & -3 & -1 & -1 & 2 & 3 \cr \hline x_2 & -3 & 1 & 0 & -2 & 3 \cr \hline y & -4 & -5 & -2 & 13 & 8 \end{array}$$ The equation is $\hat{y}=$ $+$ $x_1+$ $x_2.$