设数列an的前n项和Sn=2an-1（n+1,2,3……）,数列bn满足b1=3,bk+1=ak+bk（k=1,2……）,求数列bn的前n项
问题描述：
设数列an的前n项和Sn=2an-1（n+1,2,3……）,数列bn满足b1=3,bk+1=ak+bk（k=1,2……）,求数列bn的前n项
答
S(n-1)=2a(n-1)-1 S1=a1=2(a1)-1a1=1
an=Sn-S(n-1)=2an-2a(n-1)
an=2a(n-1)
an=a1*2^(n-1)=2^(n-1)
2.b(k+1)=2^(k-1)+bk
bk=2^(k-2)+b(k-1)
bk/(2^k)=(1/2)*(b(k-1)/(2^(k-1)))+1/4