\[x^{2} - 13x + 5 = 0\ \ \]
\[x_{1} + x_{2} = 13;\ \ \ x_{1} \cdot x_{2} = 5.\]
\[\frac{1}{x_{1}} + \frac{1}{x_{2}} = \frac{x_{2} + x_{1}}{x_{1} \cdot x_{2}} = \frac{13}{5} =\]
\[= 2\frac{3}{5} = 2,6.\]