16. For what real numbers $r$ does the system of equations
$$
\left\{\begin{aligned}
x^{2} & =y^{2} \\
(x-r)^{2}+y^{2} & =1
\end{aligned}\right.
$$
have no solutions?
16. $(-\infty,-\sqrt{2}) \cup(\sqrt{2},+\infty)$