e) $$\frac{2\sqrt{x}-3\sqrt{y}}{4x-9y} = \frac{2\sqrt{x}-3\sqrt{y}}{(2\sqrt{x}-3\sqrt{y})(2\sqrt{x}+3\sqrt{y})} = \frac{1}{2\sqrt{x}+3\sqrt{y}}$$
Ответ: $$\frac{1}{2\sqrt{x}+3\sqrt{y}}$$