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【323552】2023七年级数学上册 第2章 有理数2.5有理数的大小比较课时练习 (新版)华东师大

时间:2025-01-15 19:22:48 作者: 字数:3217字
简介:


有理数的大小比较

(30分钟 50 <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/48/" title="练习" class="c1" target="_blank">练习</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/848/" title="华东" class="c1" target="_blank">华东</a> <a href="/tags/852/" title="有理数" class="c1" target="_blank">有理数</a> )

一、选择题(每小题4,12)

1.(河南中考)下列各数中,最小的数是 (  )

A.-2    B.-0.1    C.0    D.|-1|

2.(贵阳中考)下列整数中,小于-3的整数是 <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/48/" title="练习" class="c1" target="_blank">练习</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/848/" title="华东" class="c1" target="_blank">华东</a> <a href="/tags/852/" title="有理数" class="c1" target="_blank">有理数</a>  (  )

A.-4    B.-2    C.2    D.3

3.-1<x<0,x, <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/48/" title="练习" class="c1" target="_blank">练习</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/848/" title="华东" class="c1" target="_blank">华东</a> <a href="/tags/852/" title="有理数" class="c1" target="_blank">有理数</a> ,-x的大小关系是 (  )

A.x< <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/48/" title="练习" class="c1" target="_blank">练习</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/848/" title="华东" class="c1" target="_blank">华东</a> <a href="/tags/852/" title="有理数" class="c1" target="_blank">有理数</a> <-x B.-x<x< <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/48/" title="练习" class="c1" target="_blank">练习</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/848/" title="华东" class="c1" target="_blank">华东</a> <a href="/tags/852/" title="有理数" class="c1" target="_blank">有理数</a>

C. <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/48/" title="练习" class="c1" target="_blank">练习</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/848/" title="华东" class="c1" target="_blank">华东</a> <a href="/tags/852/" title="有理数" class="c1" target="_blank">有理数</a> <x<-x D. <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/48/" title="练习" class="c1" target="_blank">练习</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/848/" title="华东" class="c1" target="_blank">华东</a> <a href="/tags/852/" title="有理数" class="c1" target="_blank">有理数</a> <-x<x

二、填空题(每小题4,12)

4.用“<”“>”号填空:

(1)- <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/48/" title="练习" class="c1" target="_blank">练习</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/848/" title="华东" class="c1" target="_blank">华东</a> <a href="/tags/852/" title="有理数" class="c1" target="_blank">有理数</a> ________- <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/48/" title="练习" class="c1" target="_blank">练习</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/848/" title="华东" class="c1" target="_blank">华东</a> <a href="/tags/852/" title="有理数" class="c1" target="_blank">有理数</a> .

(2)-|- <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/48/" title="练习" class="c1" target="_blank">练习</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/848/" title="华东" class="c1" target="_blank">华东</a> <a href="/tags/852/" title="有理数" class="c1" target="_blank">有理数</a> |________-[+(- <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/48/" title="练习" class="c1" target="_blank">练习</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/848/" title="华东" class="c1" target="_blank">华东</a> <a href="/tags/852/" title="有理数" class="c1" target="_blank">有理数</a> )].

5.有理数a,b在数轴上的对应点的位置如图所示,a,b,-a,|b|的大小关系是________.

 <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/48/" title="练习" class="c1" target="_blank">练习</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/848/" title="华东" class="c1" target="_blank">华东</a> <a href="/tags/852/" title="有理数" class="c1" target="_blank">有理数</a>

6.-0.618中用数字3替换其中的一个数字后,使所得的数变大,则被替换的数字可以是________.

三、解答题(26)

7.(8)比较下列各对数的大小:

(1)- <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/48/" title="练习" class="c1" target="_blank">练习</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/848/" title="华东" class="c1" target="_blank">华东</a> <a href="/tags/852/" title="有理数" class="c1" target="_blank">有理数</a> -0.7.  (2)- <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/48/" title="练习" class="c1" target="_blank">练习</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/848/" title="华东" class="c1" target="_blank">华东</a> <a href="/tags/852/" title="有理数" class="c1" target="_blank">有理数</a> - <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/48/" title="练习" class="c1" target="_blank">练习</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/848/" title="华东" class="c1" target="_blank">华东</a> <a href="/tags/852/" title="有理数" class="c1" target="_blank">有理数</a> .

8.(8)|a|<|b|,a>0,b<0,a,b,-a,-b按由小到大的顺序排列.

【拓展延伸】

9.(10)(1)a>0,a______-a;a=0,a______-a;a<0 <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/48/" title="练习" class="c1" target="_blank">练习</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/848/" title="华东" class="c1" target="_blank">华东</a> <a href="/tags/852/" title="有理数" class="c1" target="_blank">有理数</a> ,a______-a.

(2)请仿照(1)的方法,比较a <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/48/" title="练习" class="c1" target="_blank">练习</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/848/" title="华东" class="c1" target="_blank">华东</a> <a href="/tags/852/" title="有理数" class="c1" target="_blank">有理数</a> 的大小关系.



答案解析

1.【解析】选A.因为|-1|=1,所以四个数字中|-1|最大,其次是0,剩余的两个负数,运用“两 <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/48/" title="练习" class="c1" target="_blank">练习</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/848/" title="华东" class="c1" target="_blank">华东</a> <a href="/tags/852/" title="有理数" class="c1" target="_blank">有理数</a> 个负数,绝对值大的反而小”比较大小,所以-2最小.

2.【解析】选A.因为-4<-3<-2<2 <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/48/" title="练习" class="c1" target="_blank">练习</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/848/" title="华东" class="c1" target="_blank">华东</a> <a href="/tags/852/" title="有理数" class="c1" target="_blank">有理数</a> <3,所以整数-4,-2,2,3,小于-3的整数是-4.

3.【解析】选C.-1<x<0,x- <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/48/" title="练习" class="c1" target="_blank">练习</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/848/" title="华东" class="c1" target="_blank">华东</a> <a href="/tags/852/" title="有理数" class="c1" target="_blank">有理数</a> , <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/48/" title="练习" class="c1" target="_blank">练习</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/848/" title="华东" class="c1" target="_blank">华东</a> <a href="/tags/852/" title="有理数" class="c1" target="_blank">有理数</a> =-2,-x= <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/48/" title="练习" class="c1" target="_blank">练习</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/848/" title="华东" class="c1" target="_blank">华东</a> <a href="/tags/852/" title="有理数" class="c1" target="_blank">有理数</a> ,于是可知-2<- <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/48/" title="练习" class="c1" target="_blank">练习</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/848/" title="华东" class="c1" target="_blank">华东</a> <a href="/tags/852/" title="有理数" class="c1" target="_blank">有理数</a> < <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/48/" title="练习" class="c1" target="_blank">练习</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/848/" title="华东" class="c1" target="_blank">华东</a> <a href="/tags/852/" title="有理数" class="c1" target="_blank">有理数</a> .所以x, <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/48/" title="练习" class="c1" target="_blank">练习</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/848/" title="华东" class="c1" target="_blank">华东</a> <a href="/tags/852/" title="有理数" class="c1" target="_blank">有理数</a> ,-x的大小关系是 <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/48/" title="练习" class="c1" target="_blank">练习</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/848/" title="华东" class="c1" target="_blank">华东</a> <a href="/tags/852/" title="有理数" class="c1" target="_blank">有理数</a> <x<-x.

【变式训练】比 <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/48/" title="练习" class="c1" target="_blank">练习</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/848/" title="华东" class="c1" target="_blank">华东</a> <a href="/tags/852/" title="有理数" class="c1" target="_blank">有理数</a>a2a的大小.

【解析】分三种情况讨论:

(1)a<0,a>2a.

(2)a>0,a< <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/48/" title="练习" class="c1" target="_blank">练习</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/848/" title="华东" class="c1" target="_blank">华东</a> <a href="/tags/852/" title="有理数" class="c1" target="_blank">有理数</a> 2a.

(3)a=0 <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/48/" title="练习" class="c1" target="_blank">练习</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/848/" title="华东" class="c1" target="_blank">华东</a> <a href="/tags/852/" title="有理数" class="c1" target="_blank">有理数</a> ,a=2a.

4.【解析】(1)因为|- <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/48/" title="练习" class="c1" target="_blank">练习</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/848/" title="华东" class="c1" target="_blank">华东</a> <a href="/tags/852/" title="有理数" class="c1" target="_blank">有理数</a> |= <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/48/" title="练习" class="c1" target="_blank">练习</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/848/" title="华东" class="c1" target="_blank">华东</a> <a href="/tags/852/" title="有理数" class="c1" target="_blank">有理数</a> = <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/48/" title="练习" class="c1" target="_blank">练习</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/848/" title="华东" class="c1" target="_blank">华东</a> <a href="/tags/852/" title="有理数" class="c1" target="_blank">有理数</a> ,|- <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/48/" title="练习" class="c1" target="_blank">练习</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/848/" title="华东" class="c1" target="_blank">华东</a> <a href="/tags/852/" title="有理数" class="c1" target="_blank">有理数</a> |= <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/48/" title="练习" class="c1" target="_blank">练习</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/848/" title="华东" class="c1" target="_blank">华东</a> <a href="/tags/852/" title="有理数" class="c1" target="_blank">有理数</a> = <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/48/" title="练习" class="c1" target="_blank">练习</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/848/" title="华东" class="c1" target="_blank">华东</a> <a href="/tags/852/" title="有理数" class="c1" target="_blank">有理数</a> ,从而|- <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/48/" title="练习" class="c1" target="_blank">练习</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/848/" title="华东" class="c1" target="_blank">华东</a> <a href="/tags/852/" title="有理数" class="c1" target="_blank">有理数</a> |<|- <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/48/" title="练习" class="c1" target="_blank">练习</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/848/" title="华东" class="c1" target="_blank">华东</a> <a href="/tags/852/" title="有理数" class="c1" target="_blank">有理数</a> |,所以- <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/48/" title="练习" class="c1" target="_blank">练习</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/848/" title="华东" class="c1" target="_blank">华东</a> <a href="/tags/852/" title="有理数" class="c1" target="_blank">有理数</a> >- <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/48/" title="练习" class="c1" target="_blank">练习</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/848/" title="华东" class="c1" target="_blank">华东</a> <a href="/tags/852/" title="有理数" class="c1" target="_blank">有理数</a> .

(2)分别化简两数,-|- <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/48/" title="练习" class="c1" target="_blank">练习</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/848/" title="华东" class="c1" target="_blank">华东</a> <a href="/tags/852/" title="有理数" class="c1" target="_blank">有理数</a> |=- <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/48/" title="练习" class="c1" target="_blank">练习</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/848/" title="华东" class="c1" target="_blank">华东</a> <a href="/tags/852/" title="有理数" class="c1" target="_blank">有理数</a> ,-[+(- <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/48/" title="练习" class="c1" target="_blank">练习</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/848/" title="华东" class="c1" target="_blank">华东</a> <a href="/tags/852/" title="有理数" class="c1" target="_blank">有理数</a> )]= <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/48/" title="练习" class="c1" target="_blank">练习</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/848/" title="华东" class="c1" target="_blank">华东</a> <a href="/tags/852/" title="有理数" class="c1" target="_blank">有理数</a> .因为正数大于负数,

所以-|- <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/48/" title="练习" class="c1" target="_blank">练习</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/848/" title="华东" class="c1" target="_blank">华东</a> <a href="/tags/852/" title="有理数" class="c1" target="_blank">有理数</a> |<-[+(- <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/48/" title="练习" class="c1" target="_blank">练习</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/848/" title="华东" class="c1" target="_blank">华东</a> <a href="/tags/852/" title="有理数" class="c1" target="_blank">有理数</a> )].

答案:(1)>  (2)<

 <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/48/" title="练习" class="c1" target="_blank">练习</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/848/" title="华东" class="c1" target="_blank">华东</a> <a href="/tags/852/" title="有理数" class="c1" target="_blank">有理数</a> 5.【解析】在数轴 <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/48/" title="练习" class="c1" target="_blank">练习</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/848/" title="华东" class="c1" target="_blank">华东</a> <a href="/tags/852/" title="有理数" class="c1" target="_blank">有理数</a> 上右边的数总比左边的数大,所以|b|>a>-a>b.

答案:|b|>a>-a>b

6. <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/48/" title="练习" class="c1" target="_blank">练习</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/848/" title="华东" class="c1" target="_blank">华东</a> <a href="/tags/852/" title="有理数" class="c1" target="_blank">有理数</a> 解析】-0.618中的数字68替换成3后原数都会变大.

答案:68

7.【解析】(1)因为|- <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/48/" title="练习" class="c1" target="_blank">练习</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/848/" title="华东" class="c1" target="_blank">华东</a> <a href="/tags/852/" title="有理数" class="c1" target="_blank">有理数</a> |= <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/48/" title="练习" class="c1" target="_blank">练习</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/848/" title="华东" class="c1" target="_blank">华东</a> <a href="/tags/852/" title="有理数" class="c1" target="_blank">有理数</a> = <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/48/" title="练习" class="c1" target="_blank">练习</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/848/" title="华东" class="c1" target="_blank">华东</a> <a href="/tags/852/" title="有理数" class="c1" target="_blank">有理数</a> ,|-0.7|=0.7= <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/48/" title="练习" class="c1" target="_blank">练习</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/848/" title="华东" class="c1" target="_blank">华东</a> <a href="/tags/852/" title="有理数" class="c1" target="_blank">有理数</a> ,因为 <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/48/" title="练习" class="c1" target="_blank">练习</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/848/" title="华东" class="c1" target="_blank">华东</a> <a href="/tags/852/" title="有理数" class="c1" target="_blank">有理数</a> < <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/48/" title="练习" class="c1" target="_blank">练习</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/848/" title="华东" class="c1" target="_blank">华东</a> <a href="/tags/852/" title="有理数" class="c1" target="_blank">有理数</a> ,所以- <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/48/" title="练习" class="c1" target="_blank">练习</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/848/" title="华东" class="c1" target="_blank">华东</a> <a href="/tags/852/" title="有理数" class="c1" target="_blank">有理数</a> >-0.7.

(2)|- <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/48/" title="练习" class="c1" target="_blank">练习</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/848/" title="华东" class="c1" target="_blank">华东</a> <a href="/tags/852/" title="有理数" class="c1" target="_blank">有理数</a> |= <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/48/" title="练习" class="c1" target="_blank">练习</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/848/" title="华东" class="c1" target="_blank">华东</a> <a href="/tags/852/" title="有理数" class="c1" target="_blank">有理数</a> = <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/48/" title="练习" class="c1" target="_blank">练习</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/848/" title="华东" class="c1" target="_blank">华东</a> <a href="/tags/852/" title="有理数" class="c1" target="_blank">有理数</a> = <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/48/" title="练习" class="c1" target="_blank">练习</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/848/" title="华东" class="c1" target="_blank">华东</a> <a href="/tags/852/" title="有理数" class="c1" target="_blank">有理数</a> ,

|- <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/48/" title="练习" class="c1" target="_blank">练习</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/848/" title="华东" class="c1" target="_blank">华东</a> <a href="/tags/852/" title="有理数" class="c1" target="_blank">有理数</a> |= <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/48/" title="练习" class="c1" target="_blank">练习</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/848/" title="华东" class="c1" target="_blank">华东</a> <a href="/tags/852/" title="有理数" class="c1" target="_blank">有理数</a> = <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/48/" title="练习" class="c1" target="_blank">练习</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/848/" title="华东" class="c1" target="_blank">华东</a> <a href="/tags/852/" title="有理数" class="c1" target="_blank">有理数</a> = <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/48/" title="练习" class="c1" target="_blank">练习</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/848/" title="华东" class="c1" target="_blank">华东</a> <a href="/tags/852/" title="有理数" class="c1" target="_blank">有理数</a> .

因为 <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/48/" title="练习" class="c1" target="_blank">练习</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/848/" title="华东" class="c1" target="_blank">华东</a> <a href="/tags/852/" title="有理数" class="c1" target="_blank">有理数</a> < <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/48/" title="练习" class="c1" target="_blank">练习</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/848/" title="华东" class="c1" target="_blank">华东</a> <a href="/tags/852/" title="有理数" class="c1" target="_blank">有理数</a> ,

所以|- <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/48/" title="练习" class="c1" target="_blank">练习</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/848/" title="华东" class="c1" target="_blank">华东</a> <a href="/tags/852/" title="有理数" class="c1" target="_blank">有理数</a> |<|- <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/48/" title="练习" class="c1" target="_blank">练习</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/848/" title="华东" class="c1" target="_blank">华东</a> <a href="/tags/852/" title="有理数" class="c1" target="_blank">有理数</a> |,

所以- <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/48/" title="练习" class="c1" target="_blank">练习</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/848/" title="华东" class="c1" target="_blank">华东</a> <a href="/tags/852/" title="有理数" class="c1" target="_blank">有理数</a> >- <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/48/" title="练习" class="c1" target="_blank">练习</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/848/" title="华东" class="c1" target="_blank">华东</a> <a href="/tags/852/" title="有理数" class="c1" target="_blank">有理数</a> .

8.【解析】由a>0,b<0可知,a为正数,b为负数,在数轴上表示a,b的对应点分别在原点的右边和左边;|a|<|b|可知,表示a的点比表示b的点距离原点近,首先确定a,b的位置,而表示-a,-b的点分别与表示a,b的点到原点的距离相等,从而在原点的另一侧,可以得到-a,-b的位置.可以得到表 <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/48/" title="练习" class="c1" target="_blank">练习</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/848/" title="华东" class="c1" target="_blank">华东</a> <a href="/tags/852/" title="有理数" class="c1" target="_blank">有理数</a>a,b,-a,-b的点在数轴上的位置,如图所示:

 <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/48/" title="练习" class="c1" target="_blank">练习</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/848/" title="华东" class="c1" target="_blank">华东</a> <a href="/tags/852/" title="有理数" class="c1" target="_blank">有理数</a>

因此由小到大的顺序排列为b<-a<a<-b.


【知识拓展】若a>0,b>0,|a|>|b|,a>b;

a<0,b<0,|a|>|b|,a<b;

若已知|a|>|b|,你能 <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/48/" title="练习" class="c1" target="_blank">练习</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/848/" title="华东" class="c1" target="_blank">华东</a> <a href="/tags/852/" title="有理数" class="c1" target="_blank">有理数</a> 比较ab的大小吗?

【解析】分四种情况讨论:

(1)a>0,b>0,a>b;

(2)a>0,b<0,a>b;

(3)a<0,b<0,a<b;

(4)a<0,b>0,a<b.

9.【解析】(1)> = <

(2)0<a<1,a< <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/48/" title="练习" class="c1" target="_blank">练习</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/848/" title="华东" class="c1" target="_blank">华东</a> <a href="/tags/852/" title="有理数" class="c1" target="_blank">有理数</a> ;

a=1,a= <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/48/" title="练习" class="c1" target="_blank">练习</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/848/" title="华东" class="c1" target="_blank">华东</a> <a href="/tags/852/" title="有理数" class="c1" target="_blank">有理数</a> ;a>1,a> <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/48/" title="练习" class="c1" target="_blank">练习</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/848/" title="华东" class="c1" target="_blank">华东</a> <a href="/tags/852/" title="有理数" class="c1" target="_blank">有理数</a> ;

-1<a<0,a> <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/48/" title="练习" class="c1" target="_blank">练习</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/848/" title="华东" class="c1" target="_blank">华东</a> <a href="/tags/852/" title="有理数" class="c1" target="_blank">有理数</a> ;

a=-1,a= <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/48/" title="练习" class="c1" target="_blank">练习</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/848/" title="华东" class="c1" target="_blank">华东</a> <a href="/tags/852/" title="有理数" class="c1" target="_blank">有理数</a> ;

a<-1,a< <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/48/" title="练习" class="c1" target="_blank">练习</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/848/" title="华东" class="c1" target="_blank">华东</a> <a href="/tags/852/" title="有理数" class="c1" target="_blank">有理数</a> .

3