已知数列{an}满足a1=1,an+1=2an+1(n∈N*).设bn=n(an+1)，求数列bn的前n项和

显示全部楼层 · 2012-6-21 23:07:26

可以吗刚放错了...

千问 · 2012-6-21 23:07:26

a(n+1)=2an+1..........1a(n+1)-k=2(an-k)a(n+1)=2an-2k..........2与1比较,-2k=1k=-1/2a(n+1)+1/2=2(an+1/2)an+1/2是以a1+1/2=3/2为首,2为公比的等比数列.an+1/2=3/2+2(n-1)=2n-1/2an=2n-1 ...