the method of lower and upper solutions

• 上下解方法

the method of lower and upper solutions的用法和样例：

例句

1. A existence result is obtained via upper and lower solutions method coupled with the monotone iterative technique.
   利用上下解方法结合单调迭代技巧，我们得到了解的存在性结果。
2. 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稳定性。