I'm having a problem in solving the following, but I don't know how I can proceed to proof.
Let be $z\in D_R(c)$ where $D_R(c)$ is an open disc with radius $R>0 $ and center $c\in \mathbb{C}, $ and $R\neq |c|.$ Then how to establish $\frac{(|c|^2-R^2)}{\bar{x}}\in D_R(c)?$
Thanks.