\[y = \frac{x^{2}}{x - 3} + \frac{9}{3 - x} = \frac{x^{2} - 9}{x - 3} =\]
\[= \frac{(x - 3)(x + 3)}{(x - 3)} =\]
\[= x + 3;\ \ \ x \neq 3\]