$解:由 \sqrt{a-2025}有意义可知a-2025≥0,从而a≥2025.\ $
$∵\sqrt{(2024-a)^2}+ \sqrt{a-2025}=a,\ $
$∴a-2024+ \sqrt{a-2025}=a.$
$∴\sqrt{a-2025}=2024.\ $
$∴a-2025=2024^2.\ $
$∴a=2025+2024^2.\ $
$∴\frac{a-1}{2024}=\frac{2025+2024^2-1}{2024}=\frac{2024+2024^2}{2024}=2025.$