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等比数列{an}中,若an>0且a3a7=64,a5的值为 .
等比数列{an}中,若an>0且a3a7=64,a5的值为 .
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定义算式⊗:x⊗y=x(1-y),若不等式(x-a)⊗(x+a)<1对任意x都成立,则实数a的取值范围是( )
A.-1<a<1
B.0<a<2
C.
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D.
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设a
1,a
2,a
3,a
4成等比数列,其公比为2,则
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的值为( )
A.
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131101225157519704878/SYS201311012251575197048010_ST/1.png)
B.
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C.
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D.1
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若b为实数,且a+b=2,则3
a+3
b的最小值为( )
A.18
B.6
C.2
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131101225157519704878/SYS201311012251575197048009_ST/0.png)
D.2
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若数列{a
n}满足a
1=1,
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131101225157519704878/SYS201311012251575197048008_ST/0.png)
,则此数列是( )
A.等差数列
B.等比数列
C.既是等差数列又是等比数列
D.既非等差数列又非等比数列
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在△ABC中,若
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131101225157519704878/SYS201311012251575197048007_ST/0.png)
,
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131101225157519704878/SYS201311012251575197048007_ST/1.png)
,
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131101225157519704878/SYS201311012251575197048007_ST/2.png)
,则此三角形中最大内角是( )
A.60°
B.90°
C.120°
D.150°
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