已知方程或方程组有唯一(或唯一组)实数解求参数范围的问题在国内外考试中经常出现,而学生作答时常由于考虑不全面出现扩大或缩小参数范围的错误,本文举例介绍这类问题的解答方法。例1 己知关于x的方程 (a~2-1)x~2-2(a+1)x+1=0恰有一实数解,a应取什么值(88年北京市初中竞赛题)? 解依题意有由此可得 a=1 Known equations or equations with unique (or only group) real numbers solve the problem of finding the range of parameters that often appear in domestic and foreign exams, and students often complain about incompletely expanding or narrowing the parameter range. The solution to the problem. Example 1 It is known that the equation for x (a~2-1)x~2-2(a+1)x+1=0 has exactly a real solution, what value should a be taken from (the 88th Beijing junior high school competition title)? According to the meaning of the solution, there is a = 1