【答案】
分析:(1)由
![](http://thumb2018.1010pic.com//pic6/res/gzsx/web/STSource/20131103174818352643981/SYS201311031748183526439022_DA/0.png)
=
![](http://thumb2018.1010pic.com//pic6/res/gzsx/web/STSource/20131103174818352643981/SYS201311031748183526439022_DA/1.png)
(
![](http://thumb2018.1010pic.com//pic6/res/gzsx/web/STSource/20131103174818352643981/SYS201311031748183526439022_DA/2.png)
+
![](http://thumb2018.1010pic.com//pic6/res/gzsx/web/STSource/20131103174818352643981/SYS201311031748183526439022_DA/3.png)
)知M为线段AB的中点,由M的横坐标为
![](http://thumb2018.1010pic.com//pic6/res/gzsx/web/STSource/20131103174818352643981/SYS201311031748183526439022_DA/4.png)
得x
1+x
2=1,由此可求得y
1+y
2,从而可得点M的纵坐标;
(2)根据S
n=f(
![](http://thumb2018.1010pic.com//pic6/res/gzsx/web/STSource/20131103174818352643981/SYS201311031748183526439022_DA/5.png)
)+f(
![](http://thumb2018.1010pic.com//pic6/res/gzsx/web/STSource/20131103174818352643981/SYS201311031748183526439022_DA/6.png)
)+…+f(
![](http://thumb2018.1010pic.com//pic6/res/gzsx/web/STSource/20131103174818352643981/SYS201311031748183526439022_DA/7.png)
),分别令n=2,3,4即可求得s
2,s
3,s
4;由(1)知,由
![](http://thumb2018.1010pic.com//pic6/res/gzsx/web/STSource/20131103174818352643981/SYS201311031748183526439022_DA/8.png)
,得f(
![](http://thumb2018.1010pic.com//pic6/res/gzsx/web/STSource/20131103174818352643981/SYS201311031748183526439022_DA/9.png)
)+f(
![](http://thumb2018.1010pic.com//pic6/res/gzsx/web/STSource/20131103174818352643981/SYS201311031748183526439022_DA/10.png)
)=1,从而可求得2S
n;
(3)先表示出a
n,利用裂项相消法求得T
n,分离出参数λ后转化为求函数的最值可解决,利用基本不等式可得最值;
解答:解:(1)依题意,由
![](http://thumb2018.1010pic.com//pic6/res/gzsx/web/STSource/20131103174818352643981/SYS201311031748183526439022_DA/11.png)
=
![](http://thumb2018.1010pic.com//pic6/res/gzsx/web/STSource/20131103174818352643981/SYS201311031748183526439022_DA/12.png)
(
![](http://thumb2018.1010pic.com//pic6/res/gzsx/web/STSource/20131103174818352643981/SYS201311031748183526439022_DA/13.png)
+
![](http://thumb2018.1010pic.com//pic6/res/gzsx/web/STSource/20131103174818352643981/SYS201311031748183526439022_DA/14.png)
)知M为线段AB的中点,
又因为M的横坐标为
![](http://thumb2018.1010pic.com//pic6/res/gzsx/web/STSource/20131103174818352643981/SYS201311031748183526439022_DA/15.png)
,A(x
1,y
1),B(x
2,y
2),
∴
![](http://thumb2018.1010pic.com//pic6/res/gzsx/web/STSource/20131103174818352643981/SYS201311031748183526439022_DA/16.png)
=
![](http://thumb2018.1010pic.com//pic6/res/gzsx/web/STSource/20131103174818352643981/SYS201311031748183526439022_DA/17.png)
,即x
1+x
2=1,
∴
![](http://thumb2018.1010pic.com//pic6/res/gzsx/web/STSource/20131103174818352643981/SYS201311031748183526439022_DA/18.png)
=1+log
21=1,
所以
![](http://thumb2018.1010pic.com//pic6/res/gzsx/web/STSource/20131103174818352643981/SYS201311031748183526439022_DA/19.png)
=
![](http://thumb2018.1010pic.com//pic6/res/gzsx/web/STSource/20131103174818352643981/SYS201311031748183526439022_DA/20.png)
,
即点M的横坐标为定值
![](http://thumb2018.1010pic.com//pic6/res/gzsx/web/STSource/20131103174818352643981/SYS201311031748183526439022_DA/21.png)
;
(2)
![](http://thumb2018.1010pic.com//pic6/res/gzsx/web/STSource/20131103174818352643981/SYS201311031748183526439022_DA/22.png)
=
![](http://thumb2018.1010pic.com//pic6/res/gzsx/web/STSource/20131103174818352643981/SYS201311031748183526439022_DA/23.png)
,
![](http://thumb2018.1010pic.com//pic6/res/gzsx/web/STSource/20131103174818352643981/SYS201311031748183526439022_DA/24.png)
=
![](http://thumb2018.1010pic.com//pic6/res/gzsx/web/STSource/20131103174818352643981/SYS201311031748183526439022_DA/25.png)
+
![](http://thumb2018.1010pic.com//pic6/res/gzsx/web/STSource/20131103174818352643981/SYS201311031748183526439022_DA/26.png)
=1,
![](http://thumb2018.1010pic.com//pic6/res/gzsx/web/STSource/20131103174818352643981/SYS201311031748183526439022_DA/27.png)
=
![](http://thumb2018.1010pic.com//pic6/res/gzsx/web/STSource/20131103174818352643981/SYS201311031748183526439022_DA/28.png)
+
![](http://thumb2018.1010pic.com//pic6/res/gzsx/web/STSource/20131103174818352643981/SYS201311031748183526439022_DA/29.png)
+
![](http://thumb2018.1010pic.com//pic6/res/gzsx/web/STSource/20131103174818352643981/SYS201311031748183526439022_DA/30.png)
=
![](http://thumb2018.1010pic.com//pic6/res/gzsx/web/STSource/20131103174818352643981/SYS201311031748183526439022_DA/31.png)
,
由(1)知,由
![](http://thumb2018.1010pic.com//pic6/res/gzsx/web/STSource/20131103174818352643981/SYS201311031748183526439022_DA/32.png)
,得f(
![](http://thumb2018.1010pic.com//pic6/res/gzsx/web/STSource/20131103174818352643981/SYS201311031748183526439022_DA/33.png)
)+f(
![](http://thumb2018.1010pic.com//pic6/res/gzsx/web/STSource/20131103174818352643981/SYS201311031748183526439022_DA/34.png)
)=1,
又S
n=f(
![](http://thumb2018.1010pic.com//pic6/res/gzsx/web/STSource/20131103174818352643981/SYS201311031748183526439022_DA/35.png)
)+f(
![](http://thumb2018.1010pic.com//pic6/res/gzsx/web/STSource/20131103174818352643981/SYS201311031748183526439022_DA/36.png)
)+…+f(
![](http://thumb2018.1010pic.com//pic6/res/gzsx/web/STSource/20131103174818352643981/SYS201311031748183526439022_DA/37.png)
)=f(
![](http://thumb2018.1010pic.com//pic6/res/gzsx/web/STSource/20131103174818352643981/SYS201311031748183526439022_DA/38.png)
)+f(
![](http://thumb2018.1010pic.com//pic6/res/gzsx/web/STSource/20131103174818352643981/SYS201311031748183526439022_DA/39.png)
)+…+f(
![](http://thumb2018.1010pic.com//pic6/res/gzsx/web/STSource/20131103174818352643981/SYS201311031748183526439022_DA/40.png)
),
所以2S
n=(n-1)×1,即S
n=
![](http://thumb2018.1010pic.com//pic6/res/gzsx/web/STSource/20131103174818352643981/SYS201311031748183526439022_DA/41.png)
(n∈N
*且n≥2);
(3)当n≥2时,
![](http://thumb2018.1010pic.com//pic6/res/gzsx/web/STSource/20131103174818352643981/SYS201311031748183526439022_DA/42.png)
=
![](http://thumb2018.1010pic.com//pic6/res/gzsx/web/STSource/20131103174818352643981/SYS201311031748183526439022_DA/43.png)
,
又n=1时,
![](http://thumb2018.1010pic.com//pic6/res/gzsx/web/STSource/20131103174818352643981/SYS201311031748183526439022_DA/44.png)
也适合,
所以
![](http://thumb2018.1010pic.com//pic6/res/gzsx/web/STSource/20131103174818352643981/SYS201311031748183526439022_DA/45.png)
,
∴
![](http://thumb2018.1010pic.com//pic6/res/gzsx/web/STSource/20131103174818352643981/SYS201311031748183526439022_DA/46.png)
=4(
![](http://thumb2018.1010pic.com//pic6/res/gzsx/web/STSource/20131103174818352643981/SYS201311031748183526439022_DA/47.png)
![](http://thumb2018.1010pic.com//pic6/res/gzsx/web/STSource/20131103174818352643981/SYS201311031748183526439022_DA/48.png)
)
=4(
![](http://thumb2018.1010pic.com//pic6/res/gzsx/web/STSource/20131103174818352643981/SYS201311031748183526439022_DA/49.png)
)=
![](http://thumb2018.1010pic.com//pic6/res/gzsx/web/STSource/20131103174818352643981/SYS201311031748183526439022_DA/50.png)
(n∈N*),
由
![](http://thumb2018.1010pic.com//pic6/res/gzsx/web/STSource/20131103174818352643981/SYS201311031748183526439022_DA/51.png)
≤λ
![](http://thumb2018.1010pic.com//pic6/res/gzsx/web/STSource/20131103174818352643981/SYS201311031748183526439022_DA/52.png)
恒成立(n∈N*)推得λ≥
![](http://thumb2018.1010pic.com//pic6/res/gzsx/web/STSource/20131103174818352643981/SYS201311031748183526439022_DA/53.png)
,
而
![](http://thumb2018.1010pic.com//pic6/res/gzsx/web/STSource/20131103174818352643981/SYS201311031748183526439022_DA/54.png)
=
![](http://thumb2018.1010pic.com//pic6/res/gzsx/web/STSource/20131103174818352643981/SYS201311031748183526439022_DA/55.png)
![](http://thumb2018.1010pic.com//pic6/res/gzsx/web/STSource/20131103174818352643981/SYS201311031748183526439022_DA/56.png)
=
![](http://thumb2018.1010pic.com//pic6/res/gzsx/web/STSource/20131103174818352643981/SYS201311031748183526439022_DA/57.png)
(当且仅当n=2取等号),
∴
![](http://thumb2018.1010pic.com//pic6/res/gzsx/web/STSource/20131103174818352643981/SYS201311031748183526439022_DA/58.png)
,∴λ的最小正整数为1.
点评:本题考查数列与不等式、数列与向量的综合,考查恒成立问题,考查转化思想,综合性强,难度较大.