(5) The graph of the function $f(x)=x+\frac{1}{x}$ is $C_{1}, C_{1}$ is symmetric to the point $A(2,1)$, and the symmetric graph is $C_{2}$, corresponding to the function $g(x)$.
(1) Find the analytical expression of the function $g(x)$;
(2) If the line $y=b$ intersects $C_{2}$ at only one point, find the value of $b$ and the coordinates of the intersection point;
(3) Solve the inequality: $\log _{3} g(x)<\log _{3} \frac{9}{2}$.
(5) (1) $g(x)=x-2+\frac{1}{x-4}$
(2) $b=0$, point $(3,0) ; b=4$, point $(5,4)$
(3) $\frac{9}{2}<x<6$