Решите уравнение: 1/(x+5)-1/(x+13)=2/21.

\[168 = 2x^{2} + 26x + 10x + 130\]

\[2x^{2} + 36x - 38 = 0\ \ \ \ \ \ |\ :2\]

\[x² + 18x - 19 = 0\]

\[x_{1} + x_{2} = - 18;\ \ \ \ x_{1} \cdot x_{2} = - 19\]

\[x_{1} = - 19;\ \ \ \ \ x_{2} = 1\]

\[Ответ:\ x = - 19;x = 1.\]