Question 120
Find all values of the parameter $a \in \mathbb{R}$ for which the system
$$
\left\{\begin{array}{c}
y=\sqrt{5+4x-x^{2}}+2 \\
y=\sqrt{9-a^{2}+2a x-x^{2}}+a
\end{array}\right.
$$
has exactly one solution in $\mathbb{R} \times \mathbb{R}$.
$$
\left\{\begin{array}{c}
y=\sqrt{5+4x-x^{2}}+2 \\
y=\sqrt{9-a^{2}+2a x-x^{2}}+a
\end{array}\right.
$$
has exactly one solution in $\mathbb{R} \times \mathbb{R}$.