Reading this paper, I am trying to follow the calculation, but I cannot understand this equation:
$$ (X - FG^T)(X^T - GF^T) = X^TX -2F^TXG + G^TGF^TF $$
where $X$, $G$, $F$ are positive matrices.
Can someone please help me with the steps to derive the right-side from the left-side?