upper and lower solutions method的用法和樣例：
例句
- A existence result is obtained via upper and lower solutions method coupled with the monotone iterative technique.
利用上下解方法結合單調迭代技巧，我們得到了解的存在性結果。 - The boundedness and stability of the solutions are established by the upper-lower solution method.
采用上下解方法，建立了其解的有界性和穩定性。
