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1、5.2 不等式的基本性质教学目标1、使学生掌握和理解不等式的三条基本性质.2、培养学生观察、分析、比较的能力，会运用不等式的基本性质进行不等式的变形，提高他们灵活地运用所学知识解题的能力教学重点与难点教学重点：不等式的三条基本性质的运用.教学难点：不等式的基本性质3 的运用和不等式的变形以及范例要比较两个代数式的大小的几种方法，学生缺乏这方面的经验，这些是本节教学的难点.教法和学法操练合作发现总结式教学法操练合作发现归纳应用总结教学过程一、从学生原有的认知结构提出问题,练习问题，解决问题，总结结论。1.用“、=“完成下列填空：（1）如果 a-9，而-9 3，那么 a_3。（2）如果 a-9，而
2、-9-13，那么 a_-13。你发现了什么？你还可以再举例吗？试一试！能得到什么结论？不等式的基本性质：若 ab，b c，则 ac，这个性质也叫做不等式的传递性。2.通过实验观察，用“、=“完成下列填空：85 825210 7 10272你发现了什么？试一试！你能得到什么结论？通过观察和举实例合作学习，完成下列两个问题，并自己判断前面的猜想的结论是否正确？(1)已知 a b 和 b c，在数轴上表示如图：a b c 由数轴上a 和 c 的位置关系，你能得到什么结论？(2)若 a b，则 a+c和 b+c 哪个较大，a-c和 b-c呢？请用数轴上点的位置关系加以说明。不等式的基本性质2：不等式的
3、两边都加上（或减去）同一个数，所得的不等式仍成立。你总结出来了吗？5g 2g 做一做1.用适当的不等号填空：（1）0 1，a a+1（不等式的基本性质2）（2）(a-1)2 0 (a-1)2-2 -2（不等式的基本性质2）.a,b两个实数在数轴上的对应点如图所示：用“”或“”号填空：(1)a b;(2)a b;(3)a+b 0 (4)a-b 0 (5)a+b a-b (6)ab a b o a 3.通过计算，用“、=“完成下列填空：2 3 2（-1）3（-1）25 35 2（-5）3 （-5）21/2 31/2 2（-1/2）3（-1/2）你发现了什么？你还可以再举例吗？试一试！你又有什么样的
4、结论呢？-2 -3 -2（-1）-3（-1）-25 -35 -2（-5）-3 （-5）-21/2 -31/2 ，-2（-1/2）-3（-1/2）不等式的基本性质3：不等式的两边都乘（或都除以）同一个正数，所得的不等式仍成立；不等号的方向 不变。不等式的两边都乘（或都除以）同一个负数，必须把不等号的方向 改变，所得的不等式成立。再做一做我国于 12 月 11 日正式加入世界贸易组织（WTO）。加入前，产品A 的进口税超过产品B 的进口税的 1 倍以上；加入后，这两种产品的进口税都下调了15%。你认为加入后产品A的进口税仍超过产品B的进口税的1 倍以上吗？请说明理由。二、对学生刚学的知识进行巩固应
5、用1.范例讲解：已知a 0，试比较 2a 与 a 的大小解法一：举实例法解法二：数轴表示法解法三：应用性质2 移项法2.课内练习：书本P：106 3.探究活动：比较等式与不等式的基本性质文档编码:CQ9V2B3X10K4 HJ6V1Z9S1R4 ZI3M2F9L9N3文档编码:CQ9V2B3X10K4 HJ6V1Z9S1R4 ZI3M2F9L9N3文档编码:CQ9V2B3X10K4 HJ6V1Z9S1R4 ZI3M2F9L9N3文档编码:CQ9V2B3X10K4 HJ6V1Z9S1R4 ZI3M2F9L9N3文档编码:CQ9V2B3X10K4 HJ6V1Z9S1R4 ZI3M2F9L9N3文档
6、编码:CQ9V2B3X10K4 HJ6V1Z9S1R4 ZI3M2F9L9N3文档编码:CQ9V2B3X10K4 HJ6V1Z9S1R4 ZI3M2F9L9N3文档编码:CQ9V2B3X10K4 HJ6V1Z9S1R4 ZI3M2F9L9N3文档编码:CQ9V2B3X10K4 HJ6V1Z9S1R4 ZI3M2F9L9N3文档编码:CQ9V2B3X10K4 HJ6V1Z9S1R4 ZI3M2F9L9N3文档编码:CQ9V2B3X10K4 HJ6V1Z9S1R4 ZI3M2F9L9N3文档编码:CQ9V2B3X10K4 HJ6V1Z9S1R4 ZI3M2F9L9N3文档编码:CQ9V2B3X10
7、K4 HJ6V1Z9S1R4 ZI3M2F9L9N3文档编码:CQ9V2B3X10K4 HJ6V1Z9S1R4 ZI3M2F9L9N3文档编码:CQ9V2B3X10K4 HJ6V1Z9S1R4 ZI3M2F9L9N3文档编码:CQ9V2B3X10K4 HJ6V1Z9S1R4 ZI3M2F9L9N3文档编码:CQ9V2B3X10K4 HJ6V1Z9S1R4 ZI3M2F9L9N3文档编码:CQ9V2B3X10K4 HJ6V1Z9S1R4 ZI3M2F9L9N3文档编码:CQ9V2B3X10K4 HJ6V1Z9S1R4 ZI3M2F9L9N3文档编码:CQ9V2B3X10K4 HJ6V1Z9S1R
8、4 ZI3M2F9L9N3文档编码:CQ9V2B3X10K4 HJ6V1Z9S1R4 ZI3M2F9L9N3文档编码:CQ9V2B3X10K4 HJ6V1Z9S1R4 ZI3M2F9L9N3文档编码:CQ9V2B3X10K4 HJ6V1Z9S1R4 ZI3M2F9L9N3文档编码:CQ9V2B3X10K4 HJ6V1Z9S1R4 ZI3M2F9L9N3文档编码:CQ9V2B3X10K4 HJ6V1Z9S1R4 ZI3M2F9L9N3文档编码:CQ9V2B3X10K4 HJ6V1Z9S1R4 ZI3M2F9L9N3文档编码:CQ9V2B3X10K4 HJ6V1Z9S1R4 ZI3M2F9L9N3
9、文档编码:CQ9V2B3X10K4 HJ6V1Z9S1R4 ZI3M2F9L9N3文档编码:CQ9V2B3X10K4 HJ6V1Z9S1R4 ZI3M2F9L9N3文档编码:CQ9V2B3X10K4 HJ6V1Z9S1R4 ZI3M2F9L9N3文档编码:CQ9V2B3X10K4 HJ6V1Z9S1R4 ZI3M2F9L9N3文档编码:CQ9V2B3X10K4 HJ6V1Z9S1R4 ZI3M2F9L9N3文档编码:CQ9V2B3X10K4 HJ6V1Z9S1R4 ZI3M2F9L9N3文档编码:CQ9V2B3X10K4 HJ6V1Z9S1R4 ZI3M2F9L9N3文档编码:CQ9V2B3X
10、10K4 HJ6V1Z9S1R4 ZI3M2F9L9N3文档编码:CQ9V2B3X10K4 HJ6V1Z9S1R4 ZI3M2F9L9N3文档编码:CQ9V2B3X10K4 HJ6V1Z9S1R4 ZI3M2F9L9N3文档编码:CQ9V2B3X10K4 HJ6V1Z9S1R4 ZI3M2F9L9N3文档编码:CQ9V2B3X10K4 HJ6V1Z9S1R4 ZI3M2F9L9N3文档编码:CQ9V2B3X10K4 HJ6V1Z9S1R4 ZI3M2F9L9N3文档编码:CQ9V2B3X10K4 HJ6V1Z9S1R4 ZI3M2F9L9N3文档编码:CQ9V2B3X10K4 HJ6V1Z9S
11、1R4 ZI3M2F9L9N3文档编码:CQ9V2B3X10K4 HJ6V1Z9S1R4 ZI3M2F9L9N3文档编码:CQ9V2B3X10K4 HJ6V1Z9S1R4 ZI3M2F9L9N3文档编码:CQ9V2B3X10K4 HJ6V1Z9S1R4 ZI3M2F9L9N3文档编码:CQ9V2B3X10K4 HJ6V1Z9S1R4 ZI3M2F9L9N3文档编码:CQ9V2B3X10K4 HJ6V1Z9S1R4 ZI3M2F9L9N3文档编码:CQ9V2B3X10K4 HJ6V1Z9S1R4 ZI3M2F9L9N3三、对这节课所学知识回顾总结1。这节课你有那些收获?2。还有哪些困惑?3。布置
12、作业：书本作业和课外练习1 当 x 取下列数值时，不等式1-5x 16 是否成立？-4.5，-4，-3，4，2.5，0，-12 用不等式表示下列数量关系：(1)x的 3 倍大于 x 的 2 倍与 5 的差；(2)y的一半与 4 的和是负数；(3)5与 a 的 4 倍的差不是正数；(4)3与 x 的 2 倍的和是正数.3 按照下列条件写出仍然成立的不等式，并说明根据不等式的哪一条基本性质：(1)m n，两边都减去3；(2)m n，两边同乘以3；(3)m n，两边同乘以-3；(4)m n，两边同乘以 m 4 下列各题的横线上填入不等号，使不等式成立并说明是根据哪一条不等式基本性质(1)若 a-3
13、9，则 a _12；(2)若-a 10，则 a_-10；(3)若 0.5a-2，则 a _-4；(4)若-a0，则 a_0。5 已知 a0，用 或-4，两边都除以不为零的-a 8用不等号填空：文档编码:CQ9V2B3X10K4 HJ6V1Z9S1R4 ZI3M2F9L9N3文档编码:CQ9V2B3X10K4 HJ6V1Z9S1R4 ZI3M2F9L9N3文档编码:CQ9V2B3X10K4 HJ6V1Z9S1R4 ZI3M2F9L9N3文档编码:CQ9V2B3X10K4 HJ6V1Z9S1R4 ZI3M2F9L9N3文档编码:CQ9V2B3X10K4 HJ6V1Z9S1R4 ZI3M2F9L9N
14、3文档编码:CQ9V2B3X10K4 HJ6V1Z9S1R4 ZI3M2F9L9N3文档编码:CQ9V2B3X10K4 HJ6V1Z9S1R4 ZI3M2F9L9N3文档编码:CQ9V2B3X10K4 HJ6V1Z9S1R4 ZI3M2F9L9N3文档编码:CQ9V2B3X10K4 HJ6V1Z9S1R4 ZI3M2F9L9N3文档编码:CQ9V2B3X10K4 HJ6V1Z9S1R4 ZI3M2F9L9N3文档编码:CQ9V2B3X10K4 HJ6V1Z9S1R4 ZI3M2F9L9N3文档编码:CQ9V2B3X10K4 HJ6V1Z9S1R4 ZI3M2F9L9N3文档编码:CQ9V2B3
15、X10K4 HJ6V1Z9S1R4 ZI3M2F9L9N3文档编码:CQ9V2B3X10K4 HJ6V1Z9S1R4 ZI3M2F9L9N3文档编码:CQ9V2B3X10K4 HJ6V1Z9S1R4 ZI3M2F9L9N3文档编码:CQ9V2B3X10K4 HJ6V1Z9S1R4 ZI3M2F9L9N3文档编码:CQ9V2B3X10K4 HJ6V1Z9S1R4 ZI3M2F9L9N3文档编码:CQ9V2B3X10K4 HJ6V1Z9S1R4 ZI3M2F9L9N3文档编码:CQ9V2B3X10K4 HJ6V1Z9S1R4 ZI3M2F9L9N3文档编码:CQ9V2B3X10K4 HJ6V1Z9
16、S1R4 ZI3M2F9L9N3文档编码:CQ9V2B3X10K4 HJ6V1Z9S1R4 ZI3M2F9L9N3文档编码:CQ9V2B3X10K4 HJ6V1Z9S1R4 ZI3M2F9L9N3文档编码:CQ9V2B3X10K4 HJ6V1Z9S1R4 ZI3M2F9L9N3文档编码:CQ9V2B3X10K4 HJ6V1Z9S1R4 ZI3M2F9L9N3文档编码:CQ9V2B3X10K4 HJ6V1Z9S1R4 ZI3M2F9L9N3文档编码:CQ9V2B3X10K4 HJ6V1Z9S1R4 ZI3M2F9L9N3文档编码:CQ9V2B3X10K4 HJ6V1Z9S1R4 ZI3M2F9L
17、9N3文档编码:CQ9V2B3X10K4 HJ6V1Z9S1R4 ZI3M2F9L9N3文档编码:CQ9V2B3X10K4 HJ6V1Z9S1R4 ZI3M2F9L9N3文档编码:CQ9V2B3X10K4 HJ6V1Z9S1R4 ZI3M2F9L9N3文档编码:CQ9V2B3X10K4 HJ6V1Z9S1R4 ZI3M2F9L9N3文档编码:CQ9V2B3X10K4 HJ6V1Z9S1R4 ZI3M2F9L9N3文档编码:CQ9V2B3X10K4 HJ6V1Z9S1R4 ZI3M2F9L9N3文档编码:CQ9V2B3X10K4 HJ6V1Z9S1R4 ZI3M2F9L9N3文档编码:CQ9V2
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19、Z9S1R4 ZI3M2F9L9N3文档编码:CQ9V2B3X10K4 HJ6V1Z9S1R4 ZI3M2F9L9N3文档编码:CQ9V2B3X10K4 HJ6V1Z9S1R4 ZI3M2F9L9N3文档编码:CQ9V2B3X10K4 HJ6V1Z9S1R4 ZI3M2F9L9N3文档编码:CQ9V2B3X10K4 HJ6V1Z9S1R4 ZI3M2F9L9N3文档编码:CQ9V2B3X10K4 HJ6V1Z9S1R4 ZI3M2F9L9N3文档编码:CQ9V2B3X10K4 HJ6V1Z9S1R4 ZI3M2F9L9N3(1)当 a-b 0 时，a_ b；(2)当 a0，b0 时，ab _0
20、；(3)当 a 0，b0 时，ab _0；(4)当 a0，b 0 时，ab _ 0；(5)若 a _ 0，b 0，则 ab 0；9 设 ab，用不等号连接下列各题中的两个代数式：(1)a-1，b-1；(2)a+2，b+2；(3)2a，2b；10用不等号填空：(1)若a-b 0，则a _ b；(2)若b 0，则a+b _ a；(3)b a 2，则(a-2)(b-2)_ 0；(2-a)(2-b)_；(2-a)(a-b)_文档编码:CQ9V2B3X10K4 HJ6V1Z9S1R4 ZI3M2F9L9N3文档编码:CQ9V2B3X10K4 HJ6V1Z9S1R4 ZI3M2F9L9N3文档编码:CQ9
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