\[к\ знаменателю\ \]
\[x^{2} - 36 = (x + 6)(x - 6);\]
\[\frac{x - 2}{x + 6} = \frac{(x - 2)(x + 6)}{(x + 6)(x - 6)} =\]
\[= \frac{(x - 2)(x - 6)}{x² - 36}\]