2an+2n
求高二数学详细过程!:已知数列an前n项和Sn=2an+2n,求...
即an=2An-1 -2 得an-2=2（an-1-2）设bn=an-2 所以b1=a1-2=s1-2=-4 bn=-4X2^（n-1）an=bn+2=-4X2^(n-1)+2 Sn-Sn-1=2an+2n-2an-1-2(n-...
a(n+1)下角标=2an+2n,,求an (注意,是2n,不是2^n,) - 百度...
a(n+1)下角标=2an+2n a(n+1)+2n=2an+2n+2n a(n+1)+2n=2(an+2n)a(n+1)+2n/(an+2n)=2 数列an+2n是一个首项为a1,公比为2的等比数列 an+2n=a1...
已知数列{an}满足:an+1=2an+2n+2,a1=2,(1)求证数列{an...
(1)an+1=2an+2n+2 an+12n+1=an2n+2,∴{an2n}是公差为2,首项为a12=1的等差数列(2)由(1)知:an2n=2n 1,∴an=(2n 1) 2n,故Sn=1×2+3×22+5×23+...
已知数列{an}满足:na1+(n - 1)a2+…+2an - 1+an=2n.(1)求{...
(1)当n=1时,a1=2,∵na1+(n-1)a2+…+2an-1+an=2n,∴(n-1)a1+(n-2)a2+…+an-1=2n-1(n≥2),两式相减得:a1+a2+…+an=2n-1.(n≥2)当n=2,a1...
a(n+1)下角标=2an+2n,,求an
得到a(n+1)/2^n=2an/2^n+2^n/2^n=an/2^(n-1)+1 所以a(n+1)/2^n-an/2^(n-1)=1 即数列{an/2^(n-1)}是等差数列,首项就是a1，公差是1 an...
求a(n+1)=2an+2n次方的通项用直接构造法算
求a(n+1)=2an+2n次方的通项用直接构造法算 我来答 1个回答 #话题# 居家防疫自救手册 让世界痛苦 2013-02-21 · 知道合伙人教育...
求数列通项公式
Sn= 2an+2n-5 (1)n=1 a1=2a1+2-5 a1=3 S(n-1)= 2a(n-1)+2(n-1)-5 (2)(1)-(2)an= 2an -2a(n-1) +2 ...
数列an满足a1=2,an+1=an+2n,则通项公式an= - - - ,前n项和...
解答:解:由题得,an=an-1+2n-1=an-2+2n-2+2n-1=an-3+2n-3+2n-2+2n-1=…=a1+21+22+…+2n-1=2+2(1 2 n 1)1 2=2n.所以前n项和Sn=21+22...
在数列{an}中,a1=2,an+1=an+2n,则an= - - - .
解答:解:∵在数列{an}中,a1=2,an+1=an+2n,∴a2-a1=2,a3-a2=4,a4-a3=6,…an+1-an=2n,∴an=a1+(a2-a1)+(a3-a2)+…+(an-an-1)=2+2+4+6+…+2...
设a1=1,an+1=2an+n2,则通项公式an= .
解：已知条件an+1＝2an＋n²可配成如下形式：a(n+1)＋(n+1)²＋2(n+1)＋3＝2﹙an＋n²＋2n＋3﹚这一步具体的配凑方法高三教师都会讲 而...