对充要条件的证明,需要从充分性、必要性两个方面进行证明,但是同学们常把对条件充分性的证明说成是证必要性,对必要性的证明说成是证充分性,两者混淆不清.有没有简单的方法正确区分呢?当然是有的.充要条件的证明题,在题的叙述方式上只有两种:①是“求证:A是B的充要条件”;②是“求证:A的 Proof of necessary and sufficient conditions needs to be proved from two aspects of adequacy and necessity. However, students often regard the proof of the sufficiency of conditions as the necessity of proof, the proof of necessity as the sufficiency of evidence, There is no easy way to distinguish between the correct? Of course there is. Proof of necessary and sufficient proof of title, there are only two ways in the narrative of the title: ① yes ”proof: A is B necessary and sufficient conditions “; ② is ” Confirmation: A’s