设数列
的前
项和为
,且
![](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)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/3c8a478678a8db5e26aa9eff0298a2b2.png)
(1)求证:数列为等差数列;
(2)设是数列
的前
项和,求
.
更新时间:2018-11-28 20:08:15
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解题方法
【推荐1】已知数列{an}的前n项和为Sn,点(n,Sn)在曲线y=
x2+
x上,数列{bn}满足bn+bn+2=2bn+1,b4=11,{bn}的前5项和为45.
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![](https://staticzujuan.xkw.com/quesimg/Upload/formula/533a7b702ada1dd80123e4041271d521.png)
(1)求{an},{bn}的通项公式;
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![](https://staticzujuan.xkw.com/quesimg/Upload/formula/214c3d9145890d08aa7563b7547f977b.png)
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【推荐2】求:
(1)已知{an}是等比数列,a1=2,a4=16.求{an}的通项公式;
(2)已知数列
的前
项和为
,若
,(
,
)求
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(1)已知{an}是等比数列,a1=2,a4=16.求{an}的通项公式;
(2)已知数列
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/63d471926f7b27322d90c82b9ce21d3d.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b6a24198bd04c29321ae5dc5a28fe421.png)
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![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e1178862958882c214c7ad4bcf31930c.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ac69e6db1df13ed64756b4f391ae9fac.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e167b43045b3297248e334c41c621b8f.png)
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【推荐1】已知数列
是公差不为零的等差数列,
,且
.
(1)求数列
的通项公式;
(2)若数列
的前n项和为
,证明:
.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/83cf38189d5cbf627d2b82ac0eb76006.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a8a0eecb5b800fce9ae10aed86ffee62.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5731f65834e58bb01c8d21a695e395ce.png)
(1)求数列
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/83cf38189d5cbf627d2b82ac0eb76006.png)
(2)若数列
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ba57c83d526ac308d1461e80fcca9f36.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f1ae9a3b0b7aeb1545b65d91aa371b3c.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f1cb91e89800a81f4d62ed75c3ace24a.png)
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【推荐2】已知数列
是等差数列,且
,
.
(1)求
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(2)设
,求数列
的前
项和
.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/63d471926f7b27322d90c82b9ce21d3d.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/59cc5d1d065355dade907b6023e19bb3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f7b77c5c73088d59e3862b9d0fd31aa2.png)
(1)求
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/63d471926f7b27322d90c82b9ce21d3d.png)
(2)设
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/eea529063e92ee77bc27219339f25ca6.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5fce83115a50f99e08e9a2db7267aeed.png)
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![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f1ae9a3b0b7aeb1545b65d91aa371b3c.png)
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