有不少问题从正面去想很难破解,就可以考虑用反证法,用反证法证明有三步: (1)假设命题结论的反面成立; (2)从这个假设出发,经过正确的推理却导出矛盾; (3)出现的矛盾说明假设不正确,从而肯定命题的结论正确. 反证法的应用广泛,若能灵活运用,则可使一些复杂的题目简捷获证,请看 There are many problems that can be difficult to solve from the front. It is possible to consider counter-evidence and prove it in three steps: (1) Assume that the opposite of the conclusion of the proposition is true; (2) From this hypothesis, the contradiction is derived through correct reasoning; (3) The contradiction shows that the assumptions are not correct, so that the conclusion of the proposition is correct. The anti-evidence method is widely used. If it can be flexibly used, it can make some complicated topics easy to obtain. Please see