Question

a1＝7,a﹙n＋1﹚＝3an^4﹙两边取对数﹚

Answer 1

令bn = log an

则

b(n+1) = log a(n+1) = log 3an^4

= log 3 + 4log an

= log 3 + 4bn

可以解得

[b(n+1) + (log 3)/3 ] = 4[bn + (log 3)/3 ]

bn + (log 3)/3 = 4^(n-1)(b1 + (log 3)/3)

剩下的就是代入的工作了