\[\frac{1^{\backslash 2a + b}}{2a - b} - \frac{1^{\backslash 2a - b}}{2a + b} =\]
\[= \frac{2a + b - 2a + b}{(2a + b)(2a - b)} = \frac{2b}{4a^{2} - b^{2}}.\]