Old Training camp No.2

[rsoldo]

Determine and draw in Gaussian plane the set:

$$S=\left\{z\in C: \left|\frac{z-2-a}{1+2\cdot \bar a-z\cdot \bar a}\right|\le1, \forall a\in C,|a| \ne 1\right\}.$$

Find those roots of tra equation $z^8=-16$ which are located in $S.$