设轮船在静水中的速度为v,该船在流水(速度为u<v)中从上游A驶往下游B,再返回A,所用的时间为T,假设u=0,即河流改为静水,该船从A至B再返回A,所用时间为t,则( )
A.![]() | B.![]() | C.![]() | D.不能确定T与![]() |
更新时间:2018-02-17 22:01:30
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【知识点】 分式加减乘除混合运算解读
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【推荐1】已知 a、b 为实数且满足 a 1,b 1 ,设 M
, N
,则下列两个结论( )
① ab 1 时,M N ;ab 1时,M N .② 若a b 0, 则M N 0.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2c21c20c385a9f19ae51c6a21bf50e97.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d389d1a373e4caca383f11362ec6c32c.png)
① ab 1 时,M N ;ab 1时,M N .② 若a b 0, 则M N 0.
A.①②都对 | B.①对②错 | C.①错②对 | D.①②都错 |
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【推荐2】代数式
中的所有字母均不为零.我们把
、
、
、
、
中的某两个字母变为其相反数后再将这两个相反数对调位置,称为第一次“相反变换”,得到代数式
,将
中的某两个字母变为其相反数后再将这两个相反数对调位置,称为第二次“相反变换”,得到
,…….例如:对
中的
、
进行一次“相反变换”,记为
相反变换,得到
,其中
相反变换和
相反变换为相同的变换.下列说法正确的个数为( )
①
在顺次进行
,
,
三次相反变换后,得
;
②若对
进行
相反变换或
相反变换后,得到相同的
,则
;
③存在经过四次不同的相反变换后,
.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/04890b62a76ef0bd5deb215cab291211.png)
![](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://staticzujuan.xkw.com/quesimg/Upload/formula/5c02bc0c74292b1e8f395f90935d3174.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/168b3e4b1d6f04226fa2687a72a268b4.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4b104090ea2ac34be58a76a4e0e95cb3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4b104090ea2ac34be58a76a4e0e95cb3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/7df1d9b712b639c8b6809c9f3ae03706.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ac047e91852b91af639feec23a9598b2.png)
![](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/4562f3225c98cf5cb11b47d98c9cc9c3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0a933fbeabc016aee6ac6abb08078f93.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4562f3225c98cf5cb11b47d98c9cc9c3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ef333f78ed0adf43fea544f05ffddef5.png)
①
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ac047e91852b91af639feec23a9598b2.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e35ec6715ddfaf4309a7982509b591d7.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/772a32802455b32a61349b20d26f5b3a.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/60b34ac3e835cce34854907e50521269.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/83128974e4f20ad8088fcaa6047f7eea.png)
②若对
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ac047e91852b91af639feec23a9598b2.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4562f3225c98cf5cb11b47d98c9cc9c3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/60b34ac3e835cce34854907e50521269.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4b104090ea2ac34be58a76a4e0e95cb3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/bfc330a9671536bc46fa244b4ceebcf9.png)
③存在经过四次不同的相反变换后,
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/709bfc1b00ec9b530e0cc97fe9b345ef.png)
A.0 | B.1 | C.2 | D.3 |
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