阅读材料,解答下列问题:
例:当
,则
,故此时
的绝对值是它本身;当
时,
,故此时
的绝对值是0;当
时,如
,则
,故此时
的绝对值是它的相反数.综上所述,一个数的绝对值要分三种情况,即
,这种分析方法渗透了数学中的分类讨论思想.请仿照图例中的分类讨论,解决下面的问题:
(1)如果
,求x的值;
(2)若数轴上表示数a的点位于
与0之间,求
的值;
(3)当
时,
的值最小,最小值是 .
例:当
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ab839d8569171afab5ed55c22013aa72.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/48672c7e9f48709ad1151033104fad07.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0a6936d370d6a238a608ca56f87198de.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3b4d795709b0abcf47bceec2250f2f9b.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ad67113db87f63c490b11cf4b3c36789.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0a6936d370d6a238a608ca56f87198de.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/9e10e1c43b86a8cd4360ca9b57232164.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b9a81e971f501d78f5560c0c3d42f0f6.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/96e54192befac8374e6b207616ec2220.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0a6936d370d6a238a608ca56f87198de.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d832325395a6f6596f79cdf8dda83cac.png)
(1)如果
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/8f4d907359e45a7eab84d84fac03e549.png)
(2)若数轴上表示数a的点位于
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/81fb134b2b48acc99213fff6ccfee65f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e0e8a18d8c7e003a6ace9bebd742f367.png)
(3)当
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/380bbacf854e30e2e747fc286d2b9997.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6a0f7037071fe62b155a2896156558cd.png)
更新时间:2023-10-04 23:26:18
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解答题-问答题
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【推荐1】已知|a|=2,|b|=4, ①若
<0,求a﹣b的值;
②若|a﹣b|=﹣(a﹣b),求a﹣b的值.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2122e3f1e76a635e58e4d54aa594c552.png)
②若|a﹣b|=﹣(a﹣b),求a﹣b的值.
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【推荐2】阅读下列材料:
,
即当
时,
;当
时,
.
根据以上结论解决下面问题:
(1)已知a,b是有理数,当
时,求
的值;
(2)已知a,b,c是有理数,当
时,求
的值;
(3)已知a,b,c是有理数,
,
,求
的值.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4bd143d04713a5e9846600f25501dff3.png)
即当
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/08115d6d9f876dea921a4d32260ff1fb.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/773b8431a724ba714edc3998a451eac9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/9e541ea2f855f981c96207070683d388.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/88982e2bb5f7fd6bca9aa7ead06bf49d.png)
根据以上结论解决下面问题:
(1)已知a,b是有理数,当
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/94ed37ee7432002cd0e0978b2012e184.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/524a8f0aec8d5e9ef76071eaff5ead6a.png)
(2)已知a,b,c是有理数,当
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/73c21bd0bd90a89b7ff5ac0eacf612a5.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/fefef55f006747897696fe614cd877a7.png)
(3)已知a,b,c是有理数,
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/9e56f4504e0f80fd031c8b5f41832e03.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/77694c11ba40ec5c2fc4f6a05e31a048.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/59b8812805bfc0218a19233298765839.png)
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【推荐3】在数轴上表示的两个数,右边的数总比左边的数大,利用此规律,我们可以求数轴上两个点之间的距离,具体方法是:用右边的数减去左边的数的差就是表示这两个数的两点之间的距离.例如:
表示
与
的差的对值,实际上也可理解为
与
两数在数轴上所对应的两点之间的距离
[操作发现]
(1)如图,数轴上表示
和
的两点之间的距离是 ;数轴上表示
和
的两点之间的距离是 ;数轴上表示
和
的两点之间的距离是 ;数轴上表示
和
的两点之间的距离是 ;
[类比探究](2)
可理解为在数轴上 和 两点之间的距离;
[拓展应用](3)若数轴上分别表示
和
的两点
和
之间的距离是
,则
;
(4)若
,则
;
(5)若数轴上表示
的点位于表示
与
的两点之间,则
;
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4dab62b9f01d45818e0788dbaf458ada.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b8860d9787671b53b1ab68b3d526f5ca.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b74eb8a7738402df52d4a97262b85ca0.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b8860d9787671b53b1ab68b3d526f5ca.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b74eb8a7738402df52d4a97262b85ca0.png)
![](https://img.xkw.com/dksih/QBM/editorImg/2023/10/21/6af8eabe-164c-4992-ba83-6ced5e21300b.png?resizew=330)
[操作发现]
(1)如图,数轴上表示
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/bdaa19de263700a15fcf213d64a8cd57.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6f8c4c029e552954bd493b49aeab82d5.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5ca7d1107389675d32b56ec097464c14.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/8b06e95b57b7a81cd81d05557a11fa92.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6dbf80cb71406fd14621139149f7ed9e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5ca7d1107389675d32b56ec097464c14.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6dbf80cb71406fd14621139149f7ed9e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a060c710d4fb153aa74cfd2418b6ffa5.png)
[类比探究](2)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/cf7a878855a0d9ba75794b784eeb35a9.png)
[拓展应用](3)若数轴上分别表示
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/294f5ba74cdf695fc9a8a8e52f421328.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b74eb8a7738402df52d4a97262b85ca0.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5963abe8f421bd99a2aaa94831a951e9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7f9e8449aad35c5d840a3395ea86df6d.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/51ed533272ac9d01f1ce3e741b034d4f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b31463b348f21711420670df9d7d03a8.png)
(4)若
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6766544a5ebfdffa51869839ac7b65ef.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/47e4d2bcf4cdaab2a07ddf3640bb7ffa.png)
(5)若数轴上表示
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0a6936d370d6a238a608ca56f87198de.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a44986287ed599f86a23cfffe788cc76.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5ca7d1107389675d32b56ec097464c14.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/8085734d4fa57a98acf4b32eda2539d0.png)
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【推荐1】已知有理数
,
,
在数轴上对应点的位置如图;
(1)
______0,
______
,
______
.(填“
”或“
”)
(2)化简:
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0a6936d370d6a238a608ca56f87198de.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2c94bb12cee76221e13f9ef955b0aab1.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/071a7e733d466949ac935b4b8ee8d183.png)
![](https://img.xkw.com/dksih/QBM/editorImg/2023/6/27/169b2763-f8aa-4b88-a9a1-bdd9a85ddbe5.png?resizew=279)
(1)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/9db8d3facff8f90f28a936fc5b3ab878.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/20d6fc9b90f370fbb27552876b650f8f.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c95b6be4554f03bf496092f1acdfbb89.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a8409329b550296446a936d97c491ca9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c95b6be4554f03bf496092f1acdfbb89.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/392cdb9d30684cce244bef94b8d861b9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4ff7942da6c3fc4005256fb1458557c0.png)
(2)化简:
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/1f46c983e9c096d3f4913efa99878d0d.png)
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【推荐2】有理数a,b,c在数轴上的位置如图所示,
![](https://img.xkw.com/dksih/QBM/2015/12/16/1573942514638848/1573942520176640/STEM/ceeb2a93be744052beb81f38f700b845.png?resizew=291)
(1)c__________0; b+c__________0;b-a__________0(用“>、<、=”填空)
(2)试化简:|b-a |-| b+c |+|c|.
![](https://img.xkw.com/dksih/QBM/2015/12/16/1573942514638848/1573942520176640/STEM/ceeb2a93be744052beb81f38f700b845.png?resizew=291)
(1)c__________0; b+c__________0;b-a__________0(用“>、<、=”填空)
(2)试化简:|b-a |-| b+c |+|c|.
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【推荐1】已知数轴上两点A,B对应的数分别为a、b,且a、满足
.
![](https://img.xkw.com/dksih/QBM/2023/2/5/3168085818900480/3170326441000960/STEM/8cef89c5a2ce4ad7b3f3873f927d10ac.png?resizew=302)
(1)如图1,如果点P和点Q分别从点A,B同时出发,都沿数轴负方向运动,点P的运动速度为每秒1个单位,点Q的运动速度为每秒4个单位,设运动的时间为t(秒).
①
,
;
②t秒以后,点P对应的数是 .点Q对应的数是 (用含t的代数式表示出来)当P、Q相遇时,点Q对应的数为 .
③设运动时间为t(单位:秒),求当点P,点Q到原点的距离相等时t的值
(2)如图2,如果点P从点A出发沿数轴的正方向以每秒4个单位的速度运动,点M、N分别是线段AP、BP的中点,在运动过程中,线段MN的长度是否为定值.如果变化,请说明理由;如果不变,请求出线段MN的长度.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c0823598160833b8ebeb5395a5ca3970.png)
![](https://img.xkw.com/dksih/QBM/2023/2/5/3168085818900480/3170326441000960/STEM/8cef89c5a2ce4ad7b3f3873f927d10ac.png?resizew=302)
(1)如图1,如果点P和点Q分别从点A,B同时出发,都沿数轴负方向运动,点P的运动速度为每秒1个单位,点Q的运动速度为每秒4个单位,设运动的时间为t(秒).
①
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/380bbacf854e30e2e747fc286d2b9997.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5ccd4162c7d09f970cb77cadacdbe521.png)
②t秒以后,点P对应的数是 .点Q对应的数是 (用含t的代数式表示出来)当P、Q相遇时,点Q对应的数为 .
③设运动时间为t(单位:秒),求当点P,点Q到原点的距离相等时t的值
(2)如图2,如果点P从点A出发沿数轴的正方向以每秒4个单位的速度运动,点M、N分别是线段AP、BP的中点,在运动过程中,线段MN的长度是否为定值.如果变化,请说明理由;如果不变,请求出线段MN的长度.
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名校
【推荐2】给出新定义如下:
,
;
例如:
,
;
根据上述知识,解下列问题:
(1)若
,
,则
______;
(2)若
,求
的值;
(3)若
,化简:
;(结果用含x的代数式表示)
(4)若
,求x的值.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c84b939e3335fe1705680037ee727b9e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/866edf3008f977cbdfef568ef19bc505.png)
例如:
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/daae20e586bf7eb502ffd5a7e1b93021.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b86c0b5d95d80457d834a5d49249e6d6.png)
根据上述知识,解下列问题:
(1)若
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/639c3d2ff5ee566fcc1b69c65712a661.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c9355031ea0b2dc9cef3777621bc6d38.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d27fc8bc0466fb4e4ed14f7fa9dc3682.png)
(2)若
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/896e71bae7af979f17ced76cfb205ff3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e349aab7489f098bcea13bd5bc99a936.png)
(3)若
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/75e1512c67e2f7696e7558b43b954641.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4aae37cac299cbe3ccac181b2175287f.png)
(4)若
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4e160e84f565e800b9d968c1b8480606.png)
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