14. The solution set of the inequality $(2+\sqrt{3})^{x}+(2-\sqrt{3})^{x}>8$ is $\qquad$ .
$$
\begin{array}{l}
\text { 14. }\left(-\infty, \log _{(2+\sqrt{3})}(4-\sqrt{15})\right) \cup \\
\left(\log _{(2+\sqrt{3})}(4+\sqrt{15}),+\infty\right) .
\end{array}
$$

Let $t=(2+\sqrt{3})^{x}>0$. Then the original inequality can be transformed into $t+\frac{1}{t}>8$.
Solving this, we get $t>4+\sqrt{15}$ or $0<t<4-\sqrt{15}$.