\[\boxed{\text{659}\text{\ (659)}\text{.}\text{\ }\text{Еуроки\ -\ ДЗ\ без\ мороки}}\]
\[\textbf{а)}\ \frac{2^{n + 2} - 2^{n - 1}}{2^{n}} = \frac{2^{n} \cdot \left( 2^{2} - 2^{- 2} \right)}{2^{n}} = 2² - \frac{1}{4} = 4 - \frac{1}{4} = 3\frac{3}{4};\]
\[\textbf{б)}\ \frac{25^{n} - 5^{2n - 1}}{5^{2n}} = \frac{5^{2n} - 5^{2n - 1}}{5^{2n}} = \frac{5^{2n} \cdot (1 - 5^{- 1})}{5^{2n}} = 1 - \frac{1}{5} = \frac{4}{5}.\]