在数学解题中,只要认真审题仔细分析,找准对策,就可少走弯路,以下几例即可说明这个道理.例1已知下列三个方程:x~2+4ax-4a+3=0,x~2+(a-1)x+a~2=0,x~3+2ax-2a=0,至少有一个方程有实根,求实数a的取值范围.分析此例从正面讨论,情况相当复杂,然而从它的反面推理,问题就变得十分简明, In the mathematical problem solving, as long as careful careful examination of careful examination, identify the countermeasures, you can take detours, the following examples illustrate this truth .Example 1 Known the following three equations: x ~ 2 +4 ax-4a +3 = 0, x ~ 2 + (a-1) x + a ~ 2 = 0, x ~ 3 + 2ax-2a = 0, at least one equation has a real root, Discussion, the situation is quite complicated, but from its negative reasoning, the problem becomes very concise,