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最近听初三复习课,一道中考题及其教学引发了笔者的思考.1.耐人寻味的中考选择题及其教学.兰州市2012年中考题:二次函数y=ax~2+bx+c(a≠0)的图象如图1所示,若|ax~2+bx+c|=k(k≠0)有两个不相等的实数根,则k的取值范围是().A.k<-3 B.k>-3C.k<3 D.k>3此题是选择题的第14题,处于倒数第二的位置.它的设置及其解法颇耐人寻味.题干给出的考点信息是二次函数的图象和性质、绝对值概念、一元二次方程根的判别,三个难点内容结合在一块,综合性强,难度大,但命题人又把它设置成选择题,且设置了A、B、C
Recently listening to the third grade review class, a middle school entrance examination questions and their teaching triggered the author’s thinking .1 intriguing choice of the test and its teaching. Lanzhou 2012 senior high school entrance examination questions: quadratic function y = ax ~ 2 + bx + c ( a ≠ 0) is shown in Figure 1. If | ax ~ 2 + bx + c | = k (k ≠ 0) has two real roots that are not equal, the range of k is () <-3 Bk> -3C.k <3 Dk> 3 This is the 14th multiple choice question, in the penultimate position. Its setting and its solution is rather intriguing. Function of the image and the nature of the absolute value of the concept of a quadratic root equation of the discriminant, the three difficult content combined with a comprehensive strong, difficult, but the proponents and set it to multiple choice, and set A, B, C.