Сократите дробь: (x^2-6xy+9y^2)/(x^2-9y^2).

\[\frac{x^{2} - 6xy + 9y^{2}}{x^{2} - 9y^{2}} =\]

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