问题
填空题
设数列{an}为等比数列，公比q=2，则
|
答案
∵q=2，
∴
=a2+3a4+5a7 a4+3a6+5a9 a1q+3a1q3+5a1q6 a1q3+3a1q5+5a1q8
=
=a1q+3a1q3+5a1q6 q2(a1q+3a1q3+5a1q6)
=1 q2
．1 4
故答案为：
．1 4
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设数列{an}为等比数列，公比q=2，则
|
∵q=2，
∴
=a2+3a4+5a7 a4+3a6+5a9 a1q+3a1q3+5a1q6 a1q3+3a1q5+5a1q8
=
=a1q+3a1q3+5a1q6 q2(a1q+3a1q3+5a1q6)
=1 q2
．1 4
故答案为：
．1 4