I need the proof of this equation

The multiple regression task is to find the best fitting hyperplane defined by w~ that minimizes the SSE: w~minSSE=i=1ni2=2=YY2=(YY)T(YY)=YTY2YTY^+Y^TY=YTY2YT(D~w~)+(D~w~)T(D~w~)=YTY2w~T(D~TY)+w~T(D~TD~)w~ Therefore, the optimal weight vector is given as w~=(D~TD~)1D~TY