2022年冀教版七上1.6《有理数的减法》word学案 .pdf

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1、名师精编优秀教案七年级数学学教案（课题：2.6 有理数的减法）滦南县姚王庄镇初级中学执笔刘伟学习目标1知识目标:会将有理数减法转换成加法计算；以及会将算式写成省略加号、括号和的形式进行简便计算。进一步认识到化归思想在数学学习中的应用.2能力目标:掌握有理数减法法则并熟练地进行有理数减法运算.3情感目标:培养逻辑思维能力和相互转化的数学思想、普遍联系的辩证唯物主义思想.学习重点、难点重点：减法法则的运用.难点：法则本身的理解与运用.学习过程一、预习导航减法是加法的逆运算,已知两个数的和与其中的一个加数,求另一个加数的运算叫做减法.小学学过的减法限于大数减小数(且两数均为正数)或正数减零,如:8

2、35,808.学习了有理数之后,我们将接触到小数减大数（两数均为正数）或负数减正数或负数减负数,如:2 5,(8)(3),(8)(3)等;这时的减法将怎样计算呢?依据减法是加法的逆运算这一原理,我们有:因为 (5)(3)8 由减法的意义知:这就是说,减去 3 就等于加上3 的相反数 3.由此可归纳出有理数的减法法则:减去一个数,等于 .若用字母a,b 表示有理数,则减法法则可表示为:ab二、合作探究、展示交流例 1计算：(1)(-3)-(-5)；(2)0-7;(3)18-(-3)；(4)(-3)-18；名师精编优秀教案(5)(-18)-(-3)；(6)0-(-18);(7)2-9;(8)(-2

3、)-(-2)例 2 引入了相反数的概念,减法先转化为加法,再省略加号和括号写成和的形式,例如(8)(3)（5）（9）=如 果 把 式 子 8 3 5 9 中 的“”号“”号 看 成 性 质 符 号,可 读 成“”的和;如果把号号看作运算符号,又可读成“”.怎样计算省略加号的代数和呢?它的步骤是:1.依据加法交换律和结合律,把同号的数合并在一起;2.分别求出相同符号的数的绝对数的和.3.求出异号两数的和.例 3 15 比 5高多少？15 比-5 高多少？三、巩固练习1计算：(1)-8-8；(2)(-8)-(-8)；(3)8-(-8)；(4)8-8；(5)0-6；(6)6-0；(7)0-(-6)；

4、(8)(-6)-02.填空(1)1865比-13 大，(2)比 0 小 4 的数是，(4)-9比数小 18，(5)-7 比-7 小 .(6)-31的绝对数的相反数与332相反数的差是 .(7)0-1+2-3+4=(8)若两数和是-20，其中一个加数是10，则另一个加数是 .(9)一个加数是1.2 的相反数，和为-2.5，另一个加数是 .(10)若被减数是6，差是-5，则减数是 .(11)比 0.7 小 7 的数是 .(12)-9与 5 的差的绝对值等于 .(13)若 a=5，b=2，且 a、b 异号，则 a-b=.文档编码:CN7X5S8N5X6 HK1Y9L10X3K6 ZT4K4M6Z3F

5、4文档编码:CN7X5S8N5X6 HK1Y9L10X3K6 ZT4K4M6Z3F4文档编码:CN7X5S8N5X6 HK1Y9L10X3K6 ZT4K4M6Z3F4文档编码:CN7X5S8N5X6 HK1Y9L10X3K6 ZT4K4M6Z3F4文档编码:CN7X5S8N5X6 HK1Y9L10X3K6 ZT4K4M6Z3F4文档编码:CN7X5S8N5X6 HK1Y9L10X3K6 ZT4K4M6Z3F4文档编码:CN7X5S8N5X6 HK1Y9L10X3K6 ZT4K4M6Z3F4文档编码:CN7X5S8N5X6 HK1Y9L10X3K6 ZT4K4M6Z3F4文档编码:CN7X5S8

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10、10X3K6 ZT4K4M6Z3F4文档编码:CN7X5S8N5X6 HK1Y9L10X3K6 ZT4K4M6Z3F4文档编码:CN7X5S8N5X6 HK1Y9L10X3K6 ZT4K4M6Z3F4文档编码:CN7X5S8N5X6 HK1Y9L10X3K6 ZT4K4M6Z3F4文档编码:CN7X5S8N5X6 HK1Y9L10X3K6 ZT4K4M6Z3F4文档编码:CN7X5S8N5X6 HK1Y9L10X3K6 ZT4K4M6Z3F4文档编码:CN7X5S8N5X6 HK1Y9L10X3K6 ZT4K4M6Z3F4文档编码:CN7X5S8N5X6 HK1Y9L10X3K6 ZT4K4M

11、6Z3F4文档编码:CN7X5S8N5X6 HK1Y9L10X3K6 ZT4K4M6Z3F4文档编码:CN7X5S8N5X6 HK1Y9L10X3K6 ZT4K4M6Z3F4文档编码:CN7X5S8N5X6 HK1Y9L10X3K6 ZT4K4M6Z3F4名师精编优秀教案(14)3.14-=.(15)若 a1，则 1-a=.(16)改写成省略加号的代数和形式：(-81)+(-41)-(-83)-(+21)-(-43)=.3.选择题(1)算式“-3+5-7+2-9”的读法是()A.3、5、7、2、9 的和 B.减 3 正 5 负 7 加 2 减 9 C.负 3、正 5、负 7、正 2、负 9的和

12、 D.负 3、5、7、2、9 的 和(2)把 10-(+4)+(-6)-(-5)写成省略括号的和是()A.10-4-6-5 B.10-4-6+5 C.10+(-4)+(-6)+5 D.10+4-6-5(3)下列说法正确的是().A.减去一个数，等于加上这个数 B.零减去一个数仍得这个数C.两个相反数相减得零D.在有理数加法或减法中，和不一定比加数大，被减数不一定比减数或差大(4)下列说法正确的是().A.两数的差一定小于被减数 B.若两数的差为0，则这两数必相等C.比-2 的相反数小2 的数是-4 D.如果两个有理数的差是正数，那么这两个数都是正数(5)设两个有理数的和为a，这两个数的差为b，

13、则 a、b 的大小关系是().A.a=b B.ab C.ab D.不能确定(6)若 x0，则 x-(-x)等于().A.-x B.0 C.2x D.-2x 4.当 a=11，b=-5，c=-3 时，求下列代数式的值：(1)a-c；(2)b-c；(3)a-b-c；(4)c-a-b5世界最高峰是珠穆朗玛峰，海拔高度是8848m，陆上最低处是位于亚洲西部的死海湖，湖面海拔高度是-392m两处高度相差多少？6分别求出数轴上两点间的距离：(1)表示数 6 的点与表示数2 的点；(2)表示数 5 的点与表示数0 的点；(3)表示数 2 的点与表示数-5 的点；(4)表示数-1 的点与表示数-6 的点7某地

14、一周内五天的最高气温与最低气温如下表，哪天的温差最大？哪天的温差最小？日期周一周二周三周四周五最低气温-1-5 2-3-9 最高气温82651文档编码:CN7X5S8N5X6 HK1Y9L10X3K6 ZT4K4M6Z3F4文档编码:CN7X5S8N5X6 HK1Y9L10X3K6 ZT4K4M6Z3F4文档编码:CN7X5S8N5X6 HK1Y9L10X3K6 ZT4K4M6Z3F4文档编码:CN7X5S8N5X6 HK1Y9L10X3K6 ZT4K4M6Z3F4文档编码:CN7X5S8N5X6 HK1Y9L10X3K6 ZT4K4M6Z3F4文档编码:CN7X5S8N5X6 HK1Y9L1

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18、L10X3K6 ZT4K4M6Z3F4文档编码:CN7X5S8N5X6 HK1Y9L10X3K6 ZT4K4M6Z3F4文档编码:CN7X5S8N5X6 HK1Y9L10X3K6 ZT4K4M6Z3F4文档编码:CN7X5S8N5X6 HK1Y9L10X3K6 ZT4K4M6Z3F4文档编码:CN7X5S8N5X6 HK1Y9L10X3K6 ZT4K4M6Z3F4文档编码:CN7X5S8N5X6 HK1Y9L10X3K6 ZT4K4M6Z3F4文档编码:CN7X5S8N5X6 HK1Y9L10X3K6 ZT4K4M6Z3F4文档编码:CN7X5S8N5X6 HK1Y9L10X3K6 ZT4K4

19、M6Z3F4文档编码:CN7X5S8N5X6 HK1Y9L10X3K6 ZT4K4M6Z3F4文档编码:CN7X5S8N5X6 HK1Y9L10X3K6 ZT4K4M6Z3F4文档编码:CN7X5S8N5X6 HK1Y9L10X3K6 ZT4K4M6Z3F4文档编码:CN7X5S8N5X6 HK1Y9L10X3K6 ZT4K4M6Z3F4文档编码:CN7X5S8N5X6 HK1Y9L10X3K6 ZT4K4M6Z3F4文档编码:CN7X5S8N5X6 HK1Y9L10X3K6 ZT4K4M6Z3F4文档编码:CN7X5S8N5X6 HK1Y9L10X3K6 ZT4K4M6Z3F4文档编码:CN

20、7X5S8N5X6 HK1Y9L10X3K6 ZT4K4M6Z3F4文档编码:CN7X5S8N5X6 HK1Y9L10X3K6 ZT4K4M6Z3F4文档编码:CN7X5S8N5X6 HK1Y9L10X3K6 ZT4K4M6Z3F4文档编码:CN7X5S8N5X6 HK1Y9L10X3K6 ZT4K4M6Z3F4文档编码:CN7X5S8N5X6 HK1Y9L10X3K6 ZT4K4M6Z3F4文档编码:CN7X5S8N5X6 HK1Y9L10X3K6 ZT4K4M6Z3F4名师精编优秀教案8填空：(1)如果 a-b=c，那么 a=_；(2)如果 a+b=c，那么 a=_；(3)如果 a+(-b

21、)=c，那么 a=_；(4)如果 a-(-b)=c，那么 a=_9用“”或“”号填空：(1)如果 a0，b0，那么 a-b_0；(2)如果 a0，b0，那么 a-b_0；(3)如果 a0，b0，|a|b|，那么 a-b_0；(4)如果 a0，b0，那么 a-(-b)_010解下列方程：(1)x+8=5；(2)x-(-7)=-3；(3)x-11=-4；(4)6+x=-1011.a=3,b-4=3,求 a-b 的值四、体会联想本节课主要运用了什么知识对减法运算转化成加法？减法的类型有哪些？进行减法运算时，应该注意什么？五、课后作业P54习题 1、3、4、5 题文档编码:CN7X5S8N5X6 HK

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25、HK1Y9L10X3K6 ZT4K4M6Z3F4文档编码:CN7X5S8N5X6 HK1Y9L10X3K6 ZT4K4M6Z3F4文档编码:CN7X5S8N5X6 HK1Y9L10X3K6 ZT4K4M6Z3F4文档编码:CN7X5S8N5X6 HK1Y9L10X3K6 ZT4K4M6Z3F4文档编码:CN7X5S8N5X6 HK1Y9L10X3K6 ZT4K4M6Z3F4文档编码:CN7X5S8N5X6 HK1Y9L10X3K6 ZT4K4M6Z3F4文档编码:CN7X5S8N5X6 HK1Y9L10X3K6 ZT4K4M6Z3F4文档编码:CN7X5S8N5X6 HK1Y9L10X3K6

26、ZT4K4M6Z3F4文档编码:CN7X5S8N5X6 HK1Y9L10X3K6 ZT4K4M6Z3F4文档编码:CN7X5S8N5X6 HK1Y9L10X3K6 ZT4K4M6Z3F4文档编码:CN7X5S8N5X6 HK1Y9L10X3K6 ZT4K4M6Z3F4文档编码:CN7X5S8N5X6 HK1Y9L10X3K6 ZT4K4M6Z3F4文档编码:CN7X5S8N5X6 HK1Y9L10X3K6 ZT4K4M6Z3F4文档编码:CN7X5S8N5X6 HK1Y9L10X3K6 ZT4K4M6Z3F4文档编码:CN7X5S8N5X6 HK1Y9L10X3K6 ZT4K4M6Z3F4文档

27、编码:CN7X5S8N5X6 HK1Y9L10X3K6 ZT4K4M6Z3F4文档编码:CN7X5S8N5X6 HK1Y9L10X3K6 ZT4K4M6Z3F4文档编码:CN7X5S8N5X6 HK1Y9L10X3K6 ZT4K4M6Z3F4文档编码:CN7X5S8N5X6 HK1Y9L10X3K6 ZT4K4M6Z3F4文档编码:CN7X5S8N5X6 HK1Y9L10X3K6 ZT4K4M6Z3F4文档编码:CN7X5S8N5X6 HK1Y9L10X3K6 ZT4K4M6Z3F4文档编码:CN7X5S8N5X6 HK1Y9L10X3K6 ZT4K4M6Z3F4文档编码:CN7X5S8N5X6 HK1Y9L10X3K6 ZT4K4M6Z3F4文档编码:CN7X5S8N5X6 HK1Y9L10X3K6 ZT4K4M6Z3F4文档编码:CN7X5S8N5X6 HK1Y9L10X3K6 ZT4K4M6Z3F4文档编码:CN7X5S8N5X6 HK1Y9L10X3K6 ZT4K4M6Z3F4