若数列{An}由A1=2,An+1=An+2n所确定,则A100等于多少
人气:284 ℃ 时间:2019-10-17 02:51:07
解答
a(n+1)=a(n)+2n = a(n) + n(n+1) - (n-1)n,
a(n+1) - n(n+1) = a(n) - (n-1)n = ...= a(1) - 0 = 2,
a(n) = 2 + (n-1)n,
a(100)=2+99*100=9902
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