19.2.2一次函数第一课时教学设计.pdf
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1、一次函数(第一课时)【教学目标】1结合具体情境理解一次函数的意义,能结合实际问题中的数量关系写出一次函数的解析式;2能辨别正比例函数与一次函数的区别与联系;【教学重难点】重点:一次函数的概念难点:含参数的一次函数求参数的值【课前准备】多媒体、图片【教学过程】()新课导入1、什么是正比例函数能举例说明吗2、购买一枝钢笔需元,付款总数y(元)随所购枝数 x(枝)的变化而变化,用解析式表示为:.3、问题:某登山队大本营所在地的气温为5,海拔每升高1km 气温下降 6登山队员由大本营向上登高xkm 时,他们所处位置的气温是 y试用解析式表示y 与 x 的关系师生共同分析:从大本营向上当海拔每升高1km
2、 时,气温从 5就减少 6,那么海拔增加xkm 时,气温从 5减少 6x因此 y 与 x 的函数关系式为:y=5-6x(x0)当然,这个函数也可表示为:y=-6x+5 (x0)当登山队员由大本营向上登高05km 时,他们所在位置气温就是当x=05 时函数 y=-6x+5的值,即 y=-6 05+5=2()这个函数叫什么函数,它与我们上节所学的正比例函数有何不同我们这节课将学习这些问题(二)知识讲解4、下列问题中,变量之间的对应关系是函数关系吗如果是,请写出函数解析式,这些函数解析式有哪些共同特征()有人发现,在 2025时蟋蟀每分钟鸣叫次数C与温度 t(单位:)有关,即C的值约是 t 的 7
3、倍与 35 的差()一种计算成年人标准体重G(单位:kg)的方法是,以厘米为单位量出身高值h,再减常数 105,所得差是 G的值()某城市的市内电话的月收费额y(单位:元)包括月租费22元和拨打电话 xmin 的计时费(按 01 元min 收取)()把一个长 10cm、宽 5cm 的长方形的长减少xcm,宽不变,长方形的面积 y(单位:cm2)随 x 的值而变化师生活动:学生先独立思考,然后小组交流,可以得到这些问题的函数解析式分别为:()C=7t-35 (20t25)()G=h-105()y=01x+22()y=-5x+50(0 x10)教师引导观察后请学生代表归纳:它们的形式与y=-6x+
4、5一样,这些函数都是常数 k 与自变量的积与常数b 的和的形式文档编码:CR2O8M4J7K8 HN5P7X7M1K1 ZE6Q8H6A1M1文档编码:CR2O8M4J7K8 HN5P7X7M1K1 ZE6Q8H6A1M1文档编码:CR2O8M4J7K8 HN5P7X7M1K1 ZE6Q8H6A1M1文档编码:CR2O8M4J7K8 HN5P7X7M1K1 ZE6Q8H6A1M1文档编码:CR2O8M4J7K8 HN5P7X7M1K1 ZE6Q8H6A1M1文档编码:CR2O8M4J7K8 HN5P7X7M1K1 ZE6Q8H6A1M1文档编码:CR2O8M4J7K8 HN5P7X7M1K1
5、ZE6Q8H6A1M1文档编码:CR2O8M4J7K8 HN5P7X7M1K1 ZE6Q8H6A1M1文档编码:CR2O8M4J7K8 HN5P7X7M1K1 ZE6Q8H6A1M1文档编码:CR2O8M4J7K8 HN5P7X7M1K1 ZE6Q8H6A1M1文档编码:CR2O8M4J7K8 HN5P7X7M1K1 ZE6Q8H6A1M1文档编码:CR2O8M4J7K8 HN5P7X7M1K1 ZE6Q8H6A1M1文档编码:CR2O8M4J7K8 HN5P7X7M1K1 ZE6Q8H6A1M1文档编码:CR2O8M4J7K8 HN5P7X7M1K1 ZE6Q8H6A1M1文档编码:CR2O
6、8M4J7K8 HN5P7X7M1K1 ZE6Q8H6A1M1文档编码:CR2O8M4J7K8 HN5P7X7M1K1 ZE6Q8H6A1M1文档编码:CR2O8M4J7K8 HN5P7X7M1K1 ZE6Q8H6A1M1文档编码:CR2O8M4J7K8 HN5P7X7M1K1 ZE6Q8H6A1M1文档编码:CR2O8M4J7K8 HN5P7X7M1K1 ZE6Q8H6A1M1文档编码:CR2O8M4J7K8 HN5P7X7M1K1 ZE6Q8H6A1M1文档编码:CR2O8M4J7K8 HN5P7X7M1K1 ZE6Q8H6A1M1文档编码:CR2O8M4J7K8 HN5P7X7M1K1
7、ZE6Q8H6A1M1文档编码:CR2O8M4J7K8 HN5P7X7M1K1 ZE6Q8H6A1M1文档编码:CR2O8M4J7K8 HN5P7X7M1K1 ZE6Q8H6A1M1文档编码:CR2O8M4J7K8 HN5P7X7M1K1 ZE6Q8H6A1M1文档编码:CR2O8M4J7K8 HN5P7X7M1K1 ZE6Q8H6A1M1文档编码:CR2O8M4J7K8 HN5P7X7M1K1 ZE6Q8H6A1M1文档编码:CR2O8M4J7K8 HN5P7X7M1K1 ZE6Q8H6A1M1文档编码:CR2O8M4J7K8 HN5P7X7M1K1 ZE6Q8H6A1M1文档编码:CR2O
8、8M4J7K8 HN5P7X7M1K1 ZE6Q8H6A1M1文档编码:CR2O8M4J7K8 HN5P7X7M1K1 ZE6Q8H6A1M1文档编码:CR2O8M4J7K8 HN5P7X7M1K1 ZE6Q8H6A1M1文档编码:CR2O8M4J7K8 HN5P7X7M1K1 ZE6Q8H6A1M1文档编码:CR2O8M4J7K8 HN5P7X7M1K1 ZE6Q8H6A1M1文档编码:CR2O8M4J7K8 HN5P7X7M1K1 ZE6Q8H6A1M1文档编码:CR2O8M4J7K8 HN5P7X7M1K1 ZE6Q8H6A1M1文档编码:CR2O8M4J7K8 HN5P7X7M1K1
9、ZE6Q8H6A1M1文档编码:CR2O8M4J7K8 HN5P7X7M1K1 ZE6Q8H6A1M1文档编码:CR2O8M4J7K8 HN5P7X7M1K1 ZE6Q8H6A1M1文档编码:CR2O8M4J7K8 HN5P7X7M1K1 ZE6Q8H6A1M1文档编码:CR2O8M4J7K8 HN5P7X7M1K1 ZE6Q8H6A1M1文档编码:CR2O8M4J7K8 HN5P7X7M1K1 ZE6Q8H6A1M1文档编码:CR2O8M4J7K8 HN5P7X7M1K1 ZE6Q8H6A1M1文档编码:CR2O8M4J7K8 HN5P7X7M1K1 ZE6Q8H6A1M1文档编码:CR2O
10、8M4J7K8 HN5P7X7M1K1 ZE6Q8H6A1M1文档编码:CR2O8M4J7K8 HN5P7X7M1K1 ZE6Q8H6A1M1文档编码:CR2O8M4J7K8 HN5P7X7M1K1 ZE6Q8H6A1M1文档编码:CR2O8M4J7K8 HN5P7X7M1K1 ZE6Q8H6A1M1师:确实如此,如果我们用b 来表示这个常数的话?这些函数形式就可以写成:y=kx+b(k0)教师出示一次函数的定义:一般地,形如 y=kx+b(k、b 是常数,k0?)的函数,?叫做一次函数教师引导学生继续思考当 b=0 时,y=kx+b 是什么函数学生思考后回答:当b=0 时,y=kx+b 即
11、y=kx所以说正比例函数是一种特殊的一次函数5、同桌合作探究:请写出若干个变量y 与 x 之间的函数解析式,让同桌判断是否是一次函数;如果是,请说出其一次项系数与常数项(三)新知应用例 1下列函数中哪些是一次函数,哪些又是正比例函数师生活动:学生先独立思考,然后小组讨论,教师根据学生讨论情况加以点拨:如(7)和(8)这两种形式需要加以整理,最后根据学生的回答情况得出答案;解:一次函数:(1)、(4)、(5)、(7)、(8)。正比例函数:(1)。文档编码:CR2O8M4J7K8 HN5P7X7M1K1 ZE6Q8H6A1M1文档编码:CR2O8M4J7K8 HN5P7X7M1K1 ZE6Q8H6
12、A1M1文档编码:CR2O8M4J7K8 HN5P7X7M1K1 ZE6Q8H6A1M1文档编码:CR2O8M4J7K8 HN5P7X7M1K1 ZE6Q8H6A1M1文档编码:CR2O8M4J7K8 HN5P7X7M1K1 ZE6Q8H6A1M1文档编码:CR2O8M4J7K8 HN5P7X7M1K1 ZE6Q8H6A1M1文档编码:CR2O8M4J7K8 HN5P7X7M1K1 ZE6Q8H6A1M1文档编码:CR2O8M4J7K8 HN5P7X7M1K1 ZE6Q8H6A1M1文档编码:CR2O8M4J7K8 HN5P7X7M1K1 ZE6Q8H6A1M1文档编码:CR2O8M4J7K8
13、 HN5P7X7M1K1 ZE6Q8H6A1M1文档编码:CR2O8M4J7K8 HN5P7X7M1K1 ZE6Q8H6A1M1文档编码:CR2O8M4J7K8 HN5P7X7M1K1 ZE6Q8H6A1M1文档编码:CR2O8M4J7K8 HN5P7X7M1K1 ZE6Q8H6A1M1文档编码:CR2O8M4J7K8 HN5P7X7M1K1 ZE6Q8H6A1M1文档编码:CR2O8M4J7K8 HN5P7X7M1K1 ZE6Q8H6A1M1文档编码:CR2O8M4J7K8 HN5P7X7M1K1 ZE6Q8H6A1M1文档编码:CR2O8M4J7K8 HN5P7X7M1K1 ZE6Q8H6
14、A1M1文档编码:CR2O8M4J7K8 HN5P7X7M1K1 ZE6Q8H6A1M1文档编码:CR2O8M4J7K8 HN5P7X7M1K1 ZE6Q8H6A1M1文档编码:CR2O8M4J7K8 HN5P7X7M1K1 ZE6Q8H6A1M1文档编码:CR2O8M4J7K8 HN5P7X7M1K1 ZE6Q8H6A1M1文档编码:CR2O8M4J7K8 HN5P7X7M1K1 ZE6Q8H6A1M1文档编码:CR2O8M4J7K8 HN5P7X7M1K1 ZE6Q8H6A1M1文档编码:CR2O8M4J7K8 HN5P7X7M1K1 ZE6Q8H6A1M1文档编码:CR2O8M4J7K8
15、 HN5P7X7M1K1 ZE6Q8H6A1M1文档编码:CR2O8M4J7K8 HN5P7X7M1K1 ZE6Q8H6A1M1文档编码:CR2O8M4J7K8 HN5P7X7M1K1 ZE6Q8H6A1M1文档编码:CR2O8M4J7K8 HN5P7X7M1K1 ZE6Q8H6A1M1文档编码:CR2O8M4J7K8 HN5P7X7M1K1 ZE6Q8H6A1M1文档编码:CR2O8M4J7K8 HN5P7X7M1K1 ZE6Q8H6A1M1文档编码:CR2O8M4J7K8 HN5P7X7M1K1 ZE6Q8H6A1M1文档编码:CR2O8M4J7K8 HN5P7X7M1K1 ZE6Q8H6
16、A1M1文档编码:CR2O8M4J7K8 HN5P7X7M1K1 ZE6Q8H6A1M1文档编码:CR2O8M4J7K8 HN5P7X7M1K1 ZE6Q8H6A1M1文档编码:CR2O8M4J7K8 HN5P7X7M1K1 ZE6Q8H6A1M1文档编码:CR2O8M4J7K8 HN5P7X7M1K1 ZE6Q8H6A1M1文档编码:CR2O8M4J7K8 HN5P7X7M1K1 ZE6Q8H6A1M1文档编码:CR2O8M4J7K8 HN5P7X7M1K1 ZE6Q8H6A1M1文档编码:CR2O8M4J7K8 HN5P7X7M1K1 ZE6Q8H6A1M1文档编码:CR2O8M4J7K8
17、 HN5P7X7M1K1 ZE6Q8H6A1M1文档编码:CR2O8M4J7K8 HN5P7X7M1K1 ZE6Q8H6A1M1文档编码:CR2O8M4J7K8 HN5P7X7M1K1 ZE6Q8H6A1M1文档编码:CR2O8M4J7K8 HN5P7X7M1K1 ZE6Q8H6A1M1文档编码:CR2O8M4J7K8 HN5P7X7M1K1 ZE6Q8H6A1M1文档编码:CR2O8M4J7K8 HN5P7X7M1K1 ZE6Q8H6A1M1文档编码:CR2O8M4J7K8 HN5P7X7M1K1 ZE6Q8H6A1M1文档编码:CR2O8M4J7K8 HN5P7X7M1K1 ZE6Q8H6
18、A1M1文档编码:CR2O8M4J7K8 HN5P7X7M1K1 ZE6Q8H6A1M1例 2、(1)若它是一次函数,求出k 和 b 的取值范围.(2)若它是正比例函数,求出k 和 b 的取值范围解:(1)若它是一次函数,得k-20 且k=-2,b 为任意实数(2)若它是正比例函数,则 k=-2,b=-1(四)、课堂练习基础巩固:1.在一次函数中,k,b 的值分别为多少2、在一次函数中,k,b 的值分别为多少1232bxkyk)(132kxxy312)(32xy文档编码:CR2O8M4J7K8 HN5P7X7M1K1 ZE6Q8H6A1M1文档编码:CR2O8M4J7K8 HN5P7X7M1K
19、1 ZE6Q8H6A1M1文档编码:CR2O8M4J7K8 HN5P7X7M1K1 ZE6Q8H6A1M1文档编码:CR2O8M4J7K8 HN5P7X7M1K1 ZE6Q8H6A1M1文档编码:CR2O8M4J7K8 HN5P7X7M1K1 ZE6Q8H6A1M1文档编码:CR2O8M4J7K8 HN5P7X7M1K1 ZE6Q8H6A1M1文档编码:CR2O8M4J7K8 HN5P7X7M1K1 ZE6Q8H6A1M1文档编码:CR2O8M4J7K8 HN5P7X7M1K1 ZE6Q8H6A1M1文档编码:CR2O8M4J7K8 HN5P7X7M1K1 ZE6Q8H6A1M1文档编码:CR
20、2O8M4J7K8 HN5P7X7M1K1 ZE6Q8H6A1M1文档编码:CR2O8M4J7K8 HN5P7X7M1K1 ZE6Q8H6A1M1文档编码:CR2O8M4J7K8 HN5P7X7M1K1 ZE6Q8H6A1M1文档编码:CR2O8M4J7K8 HN5P7X7M1K1 ZE6Q8H6A1M1文档编码:CR2O8M4J7K8 HN5P7X7M1K1 ZE6Q8H6A1M1文档编码:CR2O8M4J7K8 HN5P7X7M1K1 ZE6Q8H6A1M1文档编码:CR2O8M4J7K8 HN5P7X7M1K1 ZE6Q8H6A1M1文档编码:CR2O8M4J7K8 HN5P7X7M1K
21、1 ZE6Q8H6A1M1文档编码:CR2O8M4J7K8 HN5P7X7M1K1 ZE6Q8H6A1M1文档编码:CR2O8M4J7K8 HN5P7X7M1K1 ZE6Q8H6A1M1文档编码:CR2O8M4J7K8 HN5P7X7M1K1 ZE6Q8H6A1M1文档编码:CR2O8M4J7K8 HN5P7X7M1K1 ZE6Q8H6A1M1文档编码:CR2O8M4J7K8 HN5P7X7M1K1 ZE6Q8H6A1M1文档编码:CR2O8M4J7K8 HN5P7X7M1K1 ZE6Q8H6A1M1文档编码:CR2O8M4J7K8 HN5P7X7M1K1 ZE6Q8H6A1M1文档编码:CR
22、2O8M4J7K8 HN5P7X7M1K1 ZE6Q8H6A1M1文档编码:CR2O8M4J7K8 HN5P7X7M1K1 ZE6Q8H6A1M1文档编码:CR2O8M4J7K8 HN5P7X7M1K1 ZE6Q8H6A1M1文档编码:CR2O8M4J7K8 HN5P7X7M1K1 ZE6Q8H6A1M1文档编码:CR2O8M4J7K8 HN5P7X7M1K1 ZE6Q8H6A1M1文档编码:CR2O8M4J7K8 HN5P7X7M1K1 ZE6Q8H6A1M1文档编码:CR2O8M4J7K8 HN5P7X7M1K1 ZE6Q8H6A1M1文档编码:CR2O8M4J7K8 HN5P7X7M1K
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