已知等比数列{an}为递增数列,且a52=a10,2(an+an+2)=5an+1,则数列{an}的通项公式为_.
问题描述:
已知等比数列{an}为递增数列,且a52=a10,2(an+an+2)=5an+1,则数列{an}的通项公式为______.
答
设数列的公比为q,首项为a1,则
∵a52=a10,2(an+an+2)=5an+1,
∴(a1q4)2=a1q9,2(1+q2)=5q,
∵等比数列{an}为递增数列,
∴q=2,a1=2
∴an=2n
故答案为:an=2n