>
数学
>
在等比数列{a
n
}中,a
n
>0,(n∈N
+
)且a
3
a
6
a
9
=8,则log
2
a
2
+log
2
a
4
+log
2
a
6
+log
2
a
8
+log
2
a
10
=______.
人气:387 ℃ 时间:2020-05-16 21:04:11
解答
设等比数列的首项为a,公比为q,则a
3
a
6
a
9
=aq
2
•aq
5
•aq
8
=a
3
•q
15
=(aq
5
)
3
=2
3
=8,得aq
5
=2;
而log
2
a
2
+log
2
a
4
+log
2
a
6
+log
2
a
8
+log
2
a
10
=
log
a
2
•
a
4
•
a
6
•
a
8
•
a
10
2
=
log
(a
q
5
)
5
2
=
log
2
5
2
=5
故答案为5
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