等比数列{an}中,其公比q等比数列{an}中,其公比q

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等比数列{an}中,其公比q等比数列{an}中,其公比q
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等比数列{an}中,其公比q等比数列{an}中,其公比q
等比数列{an}中,其公比q
等比数列{an}中,其公比q

等比数列{an}中,其公比q等比数列{an}中,其公比q
a1 + a2 = 1 ,a3+ a4 = (a1+a2)*q^2 = 4
q^2 = 4
a5+ a6 = (a3+a4)*q^2 = 16

a2=q*a1,a3=(q^2)*a1,a4=(q^3)8a1,得a2+a1=1,即(q+1)*a1=1,又q^2(q+1)a1=4,所以q^2=4又因为q<0,因此q=-2.所以a1=-1,a5=-16,a6=32. a5+a6=16