\[= \frac{(a + b)\left( a + 2\sqrt{\text{ab}} + b - 2\sqrt{\text{ab}} \right)}{4ab} =\]
\[= \frac{(a + b)(a + b)}{4ab} = \frac{(a + b)^{2}}{4ab}.\]
\[= \frac{a + 2\sqrt{\text{ab}} + b}{ab \bullet \left( \sqrt{a} + \sqrt{b} \right)^{2}} =\]
\[= \frac{\left( \sqrt{a} + \sqrt{b} \right)^{2}}{ab \bullet \left( \sqrt{a} + \sqrt{b} \right)^{2}} = \frac{1}{\text{ab}}.\]