设数列{an}前n的项和为Sn,且(3-m)Sn+2man=m+3(n∈N*).其中m为常数,m≠-3且m≠0 (1)求证:{an}是等比数列; (2)若数列{an}的公比满足q=f(m)且b1=a1=1,bn=3/2f(bn−1)(n∈N
问题描述:
设数列{an}前n的项和为Sn,且(3-m)Sn+2man=m+3(n∈N*).其中m为常数,m≠-3且m≠0
(1)求证:{an}是等比数列;
(2)若数列{an}的公比满足q=f(m)且b1=a1=1,bn=
f(bn−1)(n∈N*,n≥2),求证{3 2
}为等差数列,并求bn. 1 bn
答
(1)由(3-m)Sn+2man=m+3,得(3-m)Sn+1+2man+1=m+3,两式相减,得(3+m)an+1=2man,(m≠-3)∴an+1an=2mm+3,∴{an}是等比数列.(2)由b1=a1=1,q=f(m)=2mm+3,n∈N且n≥2时,bn=32f(bn-1)=32•2bn−1bn...