1 . 给出以下四个命题:
①已知命题
;命题
.则命题
是真命题;
②命题“若
,则
有实根”的逆否命题;
③命题“面积相等的三角形全等”的否命题;
④命题“
,则
”的逆命题.
其中正确命题的序号为___________ .(把你认为正确的命题序号都填上)
①已知命题
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a2b4755ea7583e97f1d4758bf9aa7240.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/8bd51a797da1fc76a87b5aeba4d79240.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c13472bf0353e16784a22e1f890fba40.png)
②命题“若
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/347c62b44fae618a37c145b3b5d1f1db.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2d5707186257494f1fea86066f2778b5.png)
③命题“面积相等的三角形全等”的否命题;
④命题“
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e2fb40a36a293471742ce75f6b9635b8.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/10f7906f9faac3a41101e4c3cbd60414.png)
其中正确命题的序号为
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2 . 以下关于命题的说法正确的有________ (填写所有正确命题的序号).
①“若
,则函数![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f45afdf4d717bb03adac6b899c367acb.png)
在其定义域内是减函数”是真命题;
②命题“若a=0,则ab=0”的否命题是“若a≠0,则ab≠0”;
③命题“若x,y都是偶数,则x+y也是偶数”的逆命题为真命题;
④命题“若
,则
”与命题“若
,则
”等价.
①“若
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ba2c58e340ebcea00ef2a6d05a836301.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f45afdf4d717bb03adac6b899c367acb.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/37b93abe2a497b7ef3cb8c1b9de8492e.png)
②命题“若a=0,则ab=0”的否命题是“若a≠0,则ab≠0”;
③命题“若x,y都是偶数,则x+y也是偶数”的逆命题为真命题;
④命题“若
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/582ad43edf388c096e7704d92340bf75.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d5286186cb58bf265a2a96e5195d88d1.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/dab92728b35ed5798e07a2b0095bfcc1.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a27dd329517f0dd8f1d0dfade6138ed4.png)
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