(本小题满分7分)选修4-5:不等式选讲已知为正数,求证:.
求和:Sn=+++…+.
已知数列{an}满足an+1=,a1=2,求数列{an}的通项公式.
设数列{an}的前n项和Sn=2an-2n.(1)求a3,a4;(2)证明:{an+1-2an}是等比数列;(3)求{an}的通项公式.
设数列{an}的前n项和为Sn,且(3-m)Sn+2man="m+3" (n∈N*),其中m为常数,且m≠-3,m≠0.(1)求证:{an}是等比数列;(2)若数列{an}的公比q=f(m),数列{bn}满足b1=a1,bn=f(bn-1) (n∈N,n≥2),求证:为等差数列,并求bn.
数列{an}中,a1=2,a2=3,且{anan+1}是以3为公比的等比数列,记bn=a2n-1+a2n (n∈N*).(1)求a3,a4,a5,a6的值;(2)求证:{bn}是等比数列.