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求一次不等式或不等式组中参数的取值范围,在近年各地中考卷中都有出现.但从考试的情况看,同学们丢分现象较严重.下面举例介绍三种求不等式参数范围的方法,供同学们学习参考.一、利用不等式的性质例1已知关于x的不等式(1-a)x>5的解集为x<5/(1-a),则a的取值范围是().A.a>0B.a>1C.a<0D.a<1解对照已知解集,原不等式的两边同除以1-a以后,不等号的方向改变了,可知1-a<0,即a>1,故选B.
Finding the range of values of parameters in inequalities or inequalities has appeared in recent years in all the examination papers. However, from the examination situation, the students lose points more seriously. Here are three examples of ways to find the range of inequality parameters. For the students to learn reference. First, the use of the properties of inequality Example 1 is known about the x inequality (1-a) x> 5 solution set to x <5 / (1-a), then the value of a range is ( ).Aa>0B.a>1C.a<0D.a<1 The solution refers to the known solution set. After the two sides of the original inequality are divided by 1-a, the direction of the inequality sign changes. It can be seen that 1-a<0, ie, a>1, so choose B.