对于某些与不等式的求解问题,如果从正面入手较复杂,而问题的反面求解较易,则我们不妨先求解问题的反面,即先求出使原不等式的反面不等式的解集,然后再求出此集合在确定的全集中的补集即为所求,这种“正难则反”的解题策略称为“补集法”·此法在处理不等式问题时显得十分方便, For some inequalities with the solution problem, if you start from the front more complex, and the reverse side of the problem is easier to solve, then we may first solve the opposite side of the problem, that is to find the solution set of the inverse inequality of the original inequality, and then seek The complementary set of this set is determined in the determined complete set. This “what is difficult to counter” problem solving strategy is called “complementary method”. This method is very convenient when dealing with inequality problems.