Упростите выражение: 3a/(a^2-9)-2b/(ab+3b)-b/(ab-3b).

\[\frac{3a}{a^{2} - 9} - \frac{2b}{ab + 3b} - \frac{b}{ab - 3b} =\]

\[= \frac{3a^{\backslash b}}{(a - 3)(a + 3)} - \frac{2b^{\backslash a - 3}}{b(a + 3)} - \frac{b^{\backslash a + 3}}{b(a - 3)} =\]

\[= \frac{3ab - 2ab + 6b - ab - 3b}{b(a - 3)(a + 3)} = \frac{3b}{b\left( a^{2} - 9 \right)} =\]

\[= \frac{3}{a^{2} - 9}\]