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1、,10.5 一元一次不等式组,邢台市第二十五中学 李青,第一课时 解一元一次不等式组,【设计说明】,感谢您购买本产品，本页将对该模版的设计进行补充说明：,模版标题字体：方正静蕾简体、新蒂黑板报正文字体：华文细黑，字体下载后直接安装即可,一、复习引入 1、什么叫做一元一次不等式？一个未知数，未知数的次数是1，不等号两边都是整式 2、解一元一次不等式的步骤有哪些？,（1）去分母；,（2）去括号；,（3）移项；,（4）合并同类项；,(5)系数化为1,解一元一次不等式并将解集表示在数轴上上,一、回顾旧知：,二、新课引入,据悉，鹿晗的演唱会将于10月份在北京举行，由于座位位置不同演唱会的门票也不相同。,
2、门票最高价格不高于2000；最低价格不低于300；,能用不等式表示吗？,x2000，x300,不等式组：,由若干个不等式组成的一组不等式,一元一次不等式组,1.能够说出一元一次不等式组的定义并进行识别.,2.能在数轴上正确表示一元一次不等式组的解集（重点）,3.熟练求解一元一次不等式组.(重、难点）,学习目标：,一元一次不等式组：,含有同一个未知数的一元一次不等式的不等式组，叫做一元一次不等式组。,(1)不等式必须是只含有同一个未知数；(2)每个不等式必须为一元一次不等式；(3)不等式的数量至少是两个。,注意：,练一练,判断下列各不等式组是否为一元一次不等式组，并说明理由.,否,否,是,是,是
3、,是,如何求不等式组的解集呢？,此不等式组的解集为300 x2000,公共部分,什么是不等式组的解集呢？,一元一次不等式组中所有不等式解集的公共部分,求下列不等式组的解集:,不等式组的解集为 x 2；,不等式组的解集为 x 0；,写解集规律,同大取大,不等式组的解集为 xb；,(ab),求下列不等式组的解集:,不等式组的解集为 x 1；,写解集规律,不等式组的解集为 x-1。,同小取小,不等式组的解集为 xa；,(ab),求下列不等式组的解集:,不等式组的解集为 1 x 2；,写解集规律,不等式组的解集为-1x 0；,大小小大中间找,(ab),不等式组的解集为 axb；,求下列不等式组的解集:
4、,不等式组无解；,写解集规律,不等式组无解；,大大小小无解了,(ab),不等式组无解,a,a,a,b,xa,x b,。,。,a,。,。,b,。,。,b,。,。,b,一元一次不等式组的解集的规律图析,(若当 ab时),同大取大,同小取小,大小小大中间找,大大小小无解了,求不等式组解集的口诀：,同大取大同小取小大小小大中间找大大小小无解了,举手抢答：,快速确定下列不等式组的解集：,解集为 x3.5,解集为x1,无解,解不等式，得 x9解不等式，得 x1,不等式组的解集为x1,例题解析,如何解不等式组呢？,解：,1、解每个一元一次不等式,2、根据口诀写出一元一次不等式组的解集,解一元一次不等式组的一
5、般步骤：,2x-1x+1x+84x-1,解下列不等式组,试一试，相信你能行,(1),吴,蜀,KEY WORDS,KEY WORDS,.,魏,比一比：,（3）已知4a+5和2a-4的值都是负数，求a的取值范围。,吴,魏,KEY WORDS,KEY WORDS,.,蜀,吴,蜀,KEY WORDS,KEY WORDS,.,魏,吴,蜀,KEY WORDS,KEY WORDS,吴,魏,吴,KEY WORDS,KEY WORDS,蜀,魏,还有得出不等式组解集的其他方法吗？,利用口诀来试试吧,2、已知4a+5和2a-4的值都是负数，求a的取值范围。,1.能够说出一元一次不等式组的定义并进行识别.,2.能在数
6、轴上正确表示一元一次不等式组的解集（重点）,3.熟练求解一元一次不等式组.(重、难点）,学习目标：,四、,达标测评,1、下列各式中，是一元一次不等式组有哪几个？,1、（1）的解集为。,（2）的解集为。,2、不等式组 的解集为。,3、求不等式组的解集,4、试求 的整数解。,5、代数式1-2k的值不大于5，但大于-1，求k的取值范围。,结束,提高题：,解不等式组,思考：,如果 的解集是x2，那么m的取值范围是（）,A m2 B m2C m2 D m2,由特殊到一般,类比思想,KEY WORDS,KEY WORDS,.,数形结合,谢谢大家！,四、例题解析,例1.解下列不等式组：,解:解不等式，得,在
7、同一个数轴上表示不等式，的解集为,解不等式，得,所以原不等式组的解集为,0 2 4,例1:解下列不等式组,解:解不等式,得，解不等式,得，把不等式和 的解集在数轴上表示出来:,所以不等式组的解集:,解:解不等式,得，解不等式,得，把不等式和 的解集在数轴上表示出来:,这两个不等式的解集没有公共部分，所以不等式组无解。,A designer can use default text to simulate what text would look like.A designer can use default text to simulate what text would look like.
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