等比数列{an}的前n项和为Sn已知对任意的n属于N+ 点（n,Sn）均在函数y=b的x方+r 1.求r的值

题目

等比数列{an}的前n项和为Sn已知对任意的n属于N+ 点（n,Sn）均在函数y=b的x方+r 1.求r的值
当b=2时 记Bn=n+1/4an 求数列bn的前n项和Tn

答案

点（n,Sn）均在函数y=b的x方+r1.Sn=b^n+r,a1=S1=b+r,S2=a1+a2=b^2+r,a2=b^2-b,S3=a1+a2+a3=b^3+r,a3=b^3-b^2,等比数列{an},a2^2=a1*a3,r=-12.b=2,an=2^(n-1)Bn=n+1/4an =n+1/2^(n+1),等差+等比,分别求和Tn =(1+n)*n/...