\[\sqrt{a + b};\ \ a = \frac{1}{4};\ \ b = \frac{4}{9}:\]
\[\sqrt{\frac{1^{\backslash 9}}{4} + \frac{4^{\backslash 4}}{9}} = \sqrt{\frac{9 + 16}{36}} = \sqrt{\frac{25}{36}} = \frac{5}{6}.\]