下列命题中正确的个数有( )
①实数不是有理数就是无理数;
②
;
③121的平方根是
;
④在实数范围内,非负数一定是正数;
⑤两个无理数之和一定是无理数
①实数不是有理数就是无理数;
②
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b014dac8421d520c337dd8eb73d42b44.png)
③121的平方根是
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/079e21431d9f4d76fda888a231546ea0.png)
④在实数范围内,非负数一定是正数;
⑤两个无理数之和一定是无理数
A.1个 | B.2个 | C.3个 | D.4个 |
更新时间:2022-08-30 06:34:48
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【知识点】 数与式
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【推荐2】对于任意的两个实数对(a,b)和(c,d),规定(a,b)=(c,d)当且仅当a=c,b=d;运算
“
”为:
,运算“
”为:
,设
,若![](https://img.xkw.com/dksih/QBM/2014/8/29/1571844360224768/1571844365713408/STEM/f809c15581734461beec7c7fe3bdfb9d.png)
则
.
“
![](https://img.xkw.com/dksih/QBM/2014/8/29/1571844360224768/1571844365713408/STEM/d7300a9b5d444e26ac90174b3735f9ba.png)
![](https://img.xkw.com/dksih/QBM/2014/8/29/1571844360224768/1571844365713408/STEM/38e950d8a3214dc8997694ca2074f582.png)
![](https://img.xkw.com/dksih/QBM/2014/8/29/1571844360224768/1571844365713408/STEM/d7e3d289660c492d827835082a7f20a5.png)
![](https://img.xkw.com/dksih/QBM/2014/8/29/1571844360224768/1571844365713408/STEM/ee2e67ca014d41d480374119ea521c64.png)
![](https://img.xkw.com/dksih/QBM/2014/8/29/1571844360224768/1571844365713408/STEM/6f89da63255d452c9477741c1a2d83d2.png)
![](https://img.xkw.com/dksih/QBM/2014/8/29/1571844360224768/1571844365713408/STEM/f809c15581734461beec7c7fe3bdfb9d.png)
则
![](https://img.xkw.com/dksih/QBM/2014/8/29/1571844360224768/1571844365713408/STEM/c6134e845ad84249a6158e10262fb992.png)
A.![]() | B.![]() | C.![]() | D.![]() |
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