(4) Solve the equation $4^{x}+10^{x}=25^{x}$, and explain the position of $x$ on the number line (i.e., explain between which two adjacent integers $x$ lies).
$\begin{array}{l}x= \\ \log _{0.4} \frac{\sqrt{5}-1}{2}, x \in(0,1)\end{array}$