已知各项均不相等的等差数列
的前5项和为15,且
,
,
成等比数列.
(1)求数列
的通项公式;
(2)设
,求数列
的前
项和
.
![](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/3e88093a749c0d46e0ee931ecfaff925.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/daf464629fa321a6ff7401ab79f07083.png)
(1)求数列
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/83cf38189d5cbf627d2b82ac0eb76006.png)
(2)设
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/76ddd896db026c68f28343103d6eb7c1.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/57ef6d44448092ebdb9e4a49d866a749.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b6a24198bd04c29321ae5dc5a28fe421.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f1ae9a3b0b7aeb1545b65d91aa371b3c.png)
更新时间:2021-10-11 11:03:58
|
相似题推荐
【推荐1】设等差数列
公差为
,等比数列
公比为
,已知
,
,
,
.
(1)求数列
和
的通项公式;
(2)求数列
的前n项和
.
(3)求数列
的前n项和
.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b4be2164a2c67d6163faee87a10942bb.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5c02bc0c74292b1e8f395f90935d3174.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/43b7e7cd571c8cd141cbbfe5d0890bf6.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/9aa8a716a31b0f51b70fdf9bdb257909.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5518372eecda4c1ea288113b7ff4702b.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/95199fb1e3a2600c073f7277b6cc69b0.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ce76fac5342eff7ea6534f1788408e23.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f40c9b7ce7a2145770649e30cb222a43.png)
(1)求数列
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b4be2164a2c67d6163faee87a10942bb.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/43b7e7cd571c8cd141cbbfe5d0890bf6.png)
(2)求数列
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/8c2da88be606b116c847d0e3b7ba93a1.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/08eb71ecf8d733b6932f4680874dbbf3.png)
(3)求数列
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/dc859cbb353b9b21aec5cf194d6ad743.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f1ae9a3b0b7aeb1545b65d91aa371b3c.png)
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【推荐2】已知等差数列
的公差为负数,且
,若
经重新排列后依次可成等比数列,求⑴数列
的通项
;⑵数列
的前
项和
的最大值.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/83cf38189d5cbf627d2b82ac0eb76006.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2a84917c4f840f34385c1621a26e45fb.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a2274371381ed7b5b6a1b321fda954b9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/83cf38189d5cbf627d2b82ac0eb76006.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/96abfe2da27a63e6affb19a0c80236d9.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/83cf38189d5cbf627d2b82ac0eb76006.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b6a24198bd04c29321ae5dc5a28fe421.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/08eb71ecf8d733b6932f4680874dbbf3.png)
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真题
解题方法
【推荐1】设
为实数,首项为
,公差为
的等差数列
的前n项和为
,满足
+15=0.
(Ⅰ)若
=5,求
及
;
(Ⅱ)求
的取值范围.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3da2dd8d2a73a50b19abd87bb39f48f1.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e72adb45c60c2f63b46e65ff787302bf.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5c02bc0c74292b1e8f395f90935d3174.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/63d471926f7b27322d90c82b9ce21d3d.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/08eb71ecf8d733b6932f4680874dbbf3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e62e945a6b497ab492613903f01c619a.png)
(Ⅰ)若
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d27182444d3da4003680f07ec299087c.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2a48e81b54f78b96294295542b010dfb.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e72adb45c60c2f63b46e65ff787302bf.png)
(Ⅱ)求
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5c02bc0c74292b1e8f395f90935d3174.png)
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解题方法
【推荐2】在①
,②
的前7项和为77,③
这三个条件中任选一个,补充在下面问题中,并解答问题.
已知等差数列
中,
,_____________.
(1)求
的通项公式;
(2)在
中每相邻两项之间插入4个数,使它们与原数列的数构成新的等差数列
,则
是不是数列
的项?若是,它是
的第几项?若不是,
,求k的值.
注:如果选择多个条件分别解答,按第一个解答计分.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a0f63b0b8d22cc4fef52e36436544062.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/83cf38189d5cbf627d2b82ac0eb76006.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/665aac307d4581ddcd6faf978eddbc2b.png)
已知等差数列
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/83cf38189d5cbf627d2b82ac0eb76006.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/039e4fe671d61e59b96ee525c9df43e8.png)
(1)求
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/83cf38189d5cbf627d2b82ac0eb76006.png)
(2)在
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/83cf38189d5cbf627d2b82ac0eb76006.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/034ba25825c13725931c483aa47c9363.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/8a2bc7db08a8771ea47ddcb33130c937.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/83cf38189d5cbf627d2b82ac0eb76006.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/83cf38189d5cbf627d2b82ac0eb76006.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2261078f748f8a660ab14693f3ade978.png)
注:如果选择多个条件分别解答,按第一个解答计分.
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【推荐1】已知公差大于1的等差数列{an}中,a2=3,且a1+1,a3﹣1,a6﹣3成等比数列.
(1)求数列{an}的通项公式;
(2)设数列{
}的前n项和为Sn,求证:
≤Sn<
.
(1)求数列{an}的通项公式;
(2)设数列{
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5fa172af12f6033165c5820b31566b4e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4dac452fbb5ef6dd653e7fbbef639484.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f89eef3148f2d4d09379767b4af69132.png)
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【推荐2】已知
是公差不为0的等差数列,满足
,且
,
,
成等比数列.
(1)求数列
的通项公式
;
(2)设
,求数列
的前
项和
.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/83cf38189d5cbf627d2b82ac0eb76006.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ced4e381e8c3336848b8c436dbc584f3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3e88093a749c0d46e0ee931ecfaff925.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/daf464629fa321a6ff7401ab79f07083.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d7da2f386b78cdf6489efaa2f5820d3e.png)
(1)求数列
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/83cf38189d5cbf627d2b82ac0eb76006.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/96abfe2da27a63e6affb19a0c80236d9.png)
(2)设
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/cf62e018d5136fd80adbd20808bcf0e5.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/034ba25825c13725931c483aa47c9363.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b6a24198bd04c29321ae5dc5a28fe421.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f1ae9a3b0b7aeb1545b65d91aa371b3c.png)
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【推荐1】设
是等比数列,公比不为 1 .已知
,且
,
,
成等差数列.
(Ⅰ)求
的通项公式;
(Ⅱ)设数列
的前
项和为
,求
;
(Ⅲ)设
,
为数列
的前
项和,求不超过
的最大整数.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/83cf38189d5cbf627d2b82ac0eb76006.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/14835bf3f00139ccec0694d0924db795.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e72adb45c60c2f63b46e65ff787302bf.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/05b2667a6c91b720ca9b42d092c776cf.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5b6fae41755ecb64ac239a5a2d767354.png)
(Ⅰ)求
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/83cf38189d5cbf627d2b82ac0eb76006.png)
(Ⅱ)设数列
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/8b191044f5c024f377d999910b78b422.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b6a24198bd04c29321ae5dc5a28fe421.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f1ae9a3b0b7aeb1545b65d91aa371b3c.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f1ae9a3b0b7aeb1545b65d91aa371b3c.png)
(Ⅲ)设
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0d6628830ecf1115f12d8e0474eba177.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/bf83e20035c3afd6d26ebfd53d768a70.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/526d983bed8be2c14ce68d22e2a74622.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b6a24198bd04c29321ae5dc5a28fe421.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b5d7e8fc9240ae214ea4e8c0902f3c3e.png)
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【推荐2】已知等差数列
满足![](https://staticzujuan.xkw.com/quesimg/Upload/formula/982730ebe08c0dc83d36975389af60b3.png)
.
(1)求数列
的通项公式;
(2)设数列
的前n项和为Sn.
①求Sn;
②若使不等式
成立的n (
)的值恰有4个,求实数
的取值范围.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/83cf38189d5cbf627d2b82ac0eb76006.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/982730ebe08c0dc83d36975389af60b3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/52227e660b1301ddc2c2e46d21fe04da.png)
(1)求数列
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/83cf38189d5cbf627d2b82ac0eb76006.png)
(2)设数列
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ba57c83d526ac308d1461e80fcca9f36.png)
①求Sn;
②若使不等式
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ff381219d3273e5dff9bee26cf36cb17.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/36b98ef143f8159f3a7dafa1fd2f2370.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/df64046e91b047037f19e4032e3b6de3.png)
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