Сократите дробь: (ax-ay-3x+3y)/(9-a^2 ).

\[\frac{ax - ay - 3x + 3y}{9 - a^{2}} =\]

\[= \frac{a(x - y) - 3 \cdot (x - y)}{- \left( a^{2} - 9 \right)} =\]

\[= - \frac{x - y}{a + 3} = \frac{y - x}{a + 3}\]