n / b(n-1) = 2^an / 2^a(n-1) = 2^(an - a(n-1)) = 2^(3n+1 - 3(n-1) - 1)= 2^3 = 8所以bn是以8为公比的等比数列第二问,引为an = 2^n+3^n所以a1 = 2+3 = 5a2 = 4 + 9 = 13a3 = 8 +27 = 35a2/a1 = 13/5, a3/a2 = 35...
已知的an=3n+1,bn=2的an次方,求证数列｛bn}成等比数列
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