W\(_{2}\)(z) = \(\alpha\)(W\(_{4}\) - X(z))

W\(_{4}\)(z) = Z\(^{-1}\)(W\(_{2}\)(z) + X(z)

and converts them into this:

W\(_{2}\)(z) = \(\frac{\alpha (Z^{-1}-1)}{1-\alpha Z^{-1}}X(z)\)

W\(_{4}\)(z) = \(\frac{Z^{-1}(1-\alpha)}{1-\alpha Z^{-1}}X(z)\)

I must have missed something, because I can't figure out how to make that transition. Anyone who would be able to explain? Just one of them should do the trick.