$2.322 A=\sqrt{y^{2}-6 y+9}-|y-9|+2$.

Translate the above text into English, keeping the original text's line breaks and format, and output the translation result directly.

$2.322 A=\sqrt{y^{2}-6 y+9}-|y-9|+2$.
Solution. $A=\sqrt{(y-3)^{2}}-|y-9|+2=|y-3|-|y-9|+2$.

Consider 3 cases.

1) $\left\{\begin{array}{l}y9, \\ A=y-3-(y-9)+2\end{array} \Leftrightarrow\left\{\begin{array}{l}y>9, \\ A=8 .\end{array}\right.\right.$

Answer: if $y>9$, then $A=8$.