Упростите выражение: 1/(x-5)-9/(x^2-x-20).

\[\frac{1}{x - 5} - \frac{9}{x^{2} - x - 20} =\]

\[= \frac{1^{\backslash x + 4}}{x - 5} - \frac{9}{(x + 4)(x - 5)} =\]

\[= \frac{x + 4 - 9}{(x + 4)(x - 5)} =\]

\[= \frac{x - 5}{(x + 4)(x - 5)} = \frac{1}{x + 4}.\]

\[x^{2} - x - 20 = (x + 4)(x - 5)\]

\[x_{1} + x_{2} = 1;\ \ x_{1} \cdot x_{2} = - 20;\]

\[x_{1} = 5;\ \ x_{2} = - 4.\]