Let $x^{(k)}$ and $b$ be vectors and $L,\ D, \ U$ be lower, diagonal, upper triangular matrices.
We have:
$x^{(k)}=(I+D^{-1}L)^{-1}(D^{-1}b-D^{-1}Ux^{(k-1)})$ (1)
How does the following follow from (1):
$x^{(k)}=-(D+L)^{-1}Ux^{(k-1)}+(D+L)^{-1}b$