\[\frac{x + 5}{x - 5} - \frac{x - 5}{x + 5} =\]
\[= \frac{(x + 5)^{2} - (x - 5)^{2}}{(x - 5)(x + 5)} =\]
\[= \frac{20x}{x² - 25} \Longrightarrow ч.т.д.\ \ \ x \neq \pm 5.\]