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等比数列{an}中,公比q=
1
2
,且log2a1+log2a2+…+log2a10=55,则a1+a2+…+a10=______.
人气:380 ℃ 时间:2020-06-03 21:03:02
解答
∵等比数列{an}中,公比q=
1
2
,且log2a1+log2a2+…+log2a10=55=log2(a1a2…a10)=log2 (a1a105
(a1a10)5=255,a1a10=211=a12(
1
2
)
9
,故 a1=210
∴a1+a2+…+a10 =
a1(1−q10)
1−q
=
210[1−(
1
2
)
10
]
1−
1
2
=211-2,
故答案为 211-2.
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