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等比数列{an}中a2+a3=2,a5+a6=8,a6+a7=
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等比数列{an}中a2+a3=2,a5+a6=8,a6+a7=
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设该等比数列首项为a1,公比为q
则a1q+a1q^2=2①,a1q^4+a1q^5=8②
②/①得q^3=4,即q=4^(1/3)
a6+a7=a1q^5+a1q^6=q(a1q^4+a1q^5)=q(a5+a6)=8·4(1/3)
则a1q+a1q^2=2①,a1q^4+a1q^5=8②
②/①得q^3=4,即q=4^(1/3)
a6+a7=a1q^5+a1q^6=q(a1q^4+a1q^5)=q(a5+a6)=8·4(1/3)
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