Question

设数列{an}和{bn}满足a1=b1=6,a2=b2=4,a3=b3=3 ,且数列{an+1-an}是等差数列,{bn

Answer 1

（1）an=(n-6)(n-1)/2+6

bn=2^(3-n)+2

(2) sn=(n-4)*2^(2-n)+n(n+1)+16

(3) cn=[(n-6)(n-1)/2+6]*2^(1-n)

=(n^2-7n+18)/2^n

我只能做到这一步了,接下来得靠楼主自己了