数列{an}(n下标),a1=8,a4=2,且满足an+2(n+2下标)=2an+1(n+1下标)-an(n下标).求数
1个回答
a(n+2)-a(n+1)=a(n+1)-a(n)
这是一个等差数列
d=(a4-a1)/3=-2
首项为8
所以an=8-2(n-1)=10-2n
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