反证法是一种间接证法,它从“否定命题的结论”出发,通过正确的逻辑推理,推导出与已知条件、定义、公理或定理相矛盾的结果,从而“肯定这个命题真实”.下面举例加以说明,供参考.一、证明与一元二次方程有关的问题.例题1已知a>2,b>2,请判断关于x的方程.x~2-(a+b)x+ab=0与x~2-abx+(a+b)=0有没有公共根;并说明理由.分析考虑应用反证法来证明,首先假设已知的两个方程有公共根,并把公共根代入到两个方程中,得出 Proof-of-evidence is an indirect proof that proceeds from the conclusion of “negative proposition ” and derives the result contradictory to known conditions, definitions, axioms or theorems through correct logical reasoning, thus "affirming the truth of this proposition Example 1 is known a> 2, b> 2, please determine the equation on x. X ~ 2- (a + b There is no common root for x + ab = 0 and x ~ 2-abx + (a + b) = 0, and the reasons are given. The analysis considers the application of inverse proof to prove that firstly we assume that the two known equations have a common root, Root into the two equations, come to