来自郝双晖的问题
【在数列{an}中,a1=0,且对任意(k∈N*),a2k-1,a2k,a2k+1成等差数列,其公差为dk.(Ⅰ)若dk=2k,证明a2k,a2k+1,a2k+2成等比数列(k∈N*);(Ⅱ)若对任意k∈N*,a2k-1,a2k,a2k+1成等比数列,】
在数列{an}中,a1=0,且对任意(k∈N*),a2k-1,a2k,a2k+1成等差数列,其公差为dk.
(Ⅰ)若dk=2k,证明a2k,a2k+1,a2k+2成等比数列(k∈N*);
(Ⅱ)若对任意k∈N*,a2k-1,a2k,a2k+1成等比数列,其公比为qk.
(i)设q1≠1.证明{1qk−1}是等差数列;
(ii)若a2=2,证明32<2n−nk=2k2ak≤2(n≥2)
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2020-11-18 03:14