论文部分内容阅读
参变量的确定是近几年各地中考和竞赛的热点,也是初中数学中十分重要的问题,下面笔者例谈确定参变量的几种方法。一用数学定义确参变量用数学定义确定参变量的方法,只要掌握了数学定义的本质及定义中的有关特殊规定,则不难得出符合题目要求的结论。 [例1] m是什么值时,关于x的方程(m~2-1)x~2+2x-m-2=0只有一个解? 解:方程只有一个解,说明所给方程是一元一次方程,∴ m~2-1=0,即m=±1。 [例2] 若log_(2x+3)(4x-5)有意义,求x的取值。解:由对数定义知:若使原式有意义,则
The determination of the parameter variable is a hot spot in the examinations and competitions in various places in recent years, and is also a very important issue in junior high school mathematics. The following authors discuss several ways of determining the parameter variable. A method of mathematically defining a parametric variable by using a mathematical definition to determine a parametric variable, as long as one grasps the nature of the mathematical definition and the relevant special provisions in the definition, it is not difficult to draw conclusions that meet the requirements of the topic. [Example 1] When m is what value, there is only one solution to the equation x (m~2-1) x~2+2x-m-2=0 for x? Solution: There is only one solution for the equation, which means that the given equation is once The equation, ∴ m~2-1=0, ie m=±1. [Example 2] If log_(2x+3)(4x-5) is meaningful, find the value of x. Solution: Defined by the logarithm: If the original formula makes sense, then