\[\frac{x + 4}{x - 4} - \frac{x - 4}{x + 4} =\]
\[= \frac{(x + 4)^{2} - (x - 4)^{2}}{(x - 4)(x + 4)} =\]
\[= \frac{2x \cdot 3}{x^{2} - 16} = \frac{16x}{x^{2} - 16} \Longrightarrow ч.т.д.\ \ \ \]
\[x \neq \pm 4.\]