Упростите выражение: 7/(x^2-y^2)-5/(xy-x^2)-12/(x^2+xy).

\[\frac{7}{x^{2} - y^{2}} - \frac{5}{xy - x^{2}} - \frac{12}{x^{2} + xy} =\]

\[= \frac{7^{\backslash x}}{(x - y)(x + y)} + \frac{5^{\backslash x + y}}{x(x - y)} - \frac{12^{\backslash x - y}}{x(x + y)} =\]

\[= \frac{7x + 5x + 5y - 12x + 12y}{x(x - y)(x + y)} = \frac{17y}{x\left( x^{2} - y^{2} \right)}\]