Formel umstellen

$\lambda = \frac{y-z}{c-y} \ \ |\cdot(c-y) \\ \lambda c - \lambda y = y-z \ \ \ |+\lambda y +z \\ \lambda c + z = \lambda y + y \\ \lambda c + z = (\lambda + 1)y \ \ \ |:(\lambda+1) \\ \frac{\lambda c + z}{\lambda +1} = y$