Problem 3. Solve the system

$$
\left\{\begin{array}{l}
\left|x^{4}-625 x^{2}\right| \neq x^{4}-625 x^{2} \\
\left|6 x^{2}-257 x+251\right|+6 x^{2}-257 x+251=0
\end{array}\right.
$$
Answer: $[1 ; 25)$.

Solution. The original system is equivalent to the system

$$
\left\{\begin{array}{l}
x^{4}-625 x^{2}<0 \\
6 x^{2}-257 x+251 \leqslant 0
\end{array}\right.
$$

which has the solution: $[1 ; 25)$.