1 . 已知数列
是等比数列,首项为
,公比为
.
(1)求证:“如果
,
,那么
(
为正整数)”是真命题;
(2)写出(1)中命题的逆命题,判断它的是真命题还是假命题,并说明理由.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/83cf38189d5cbf627d2b82ac0eb76006.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e72adb45c60c2f63b46e65ff787302bf.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/9aa8a716a31b0f51b70fdf9bdb257909.png)
(1)求证:“如果
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/390636a89883bd64bf8da9bf8654aff9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/eda6dc559d07bc22c9a0ed1e3a6d01d2.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a1a5945ce5c2114af8c18718ca8dc899.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b6a24198bd04c29321ae5dc5a28fe421.png)
(2)写出(1)中命题的逆命题,判断它的是真命题还是假命题,并说明理由.
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2 . 求证:若a2+2ab+b2+2a+2b-3≠0,则a+b≠1.
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11-12高二上·福建三明·期中
3 . (1)写出命题“若
是偶数,则
是偶数”的否命题;并对否命题的真假给予说明.
(2)求证:“
”是“方程
无实根”的必要不充分条件.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/632244ea6931507f8656e1cc3437d392.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/20d6fc9b90f370fbb27552876b650f8f.png)
(2)求证:“
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/58b140e221ddf537b8964fff8557cca0.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2d5707186257494f1fea86066f2778b5.png)
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