5. (Fuzhou City) The equation
$$
\begin{aligned}
& (6 x+5) \cdot\left(1+\sqrt{(6 x+5)^{2}+4}\right) \\
+ & x\left(1+\sqrt{\left.x^{2}+4\right)}=0\right. \text { has the solution }
\end{aligned}
$$
5. $-\frac{5}{7}$