6.圆x2+y2-2x-5=0与圆x2+y2+2x-4y-4=0的交点为A,B,则线段AB的垂直平分线的方程是( )
A. | x+y-1=0 | B. | 2x-y+1=0 | C. | x-2y+1=0 | D. | x-y+1=0 |
4.已知定义在R上的函数$f(x)={(\frac{1}{2})^{|x-m|}}-1$(m为实数)为偶函数,记a=f(log0.53),b=f(log25),c=f(2m),则a,b,c的大小关系为( )
A. | a<b<c | B. | b<a<c | C. | c<a<b | D. | a<c<b |
1.{an}是首项为1的等比数列,Sn为{an}的前n项和,S6=9S3,则a7=( )
A. | 32 | B. | 64 | C. | $\frac{81}{32}$ | D. | $\frac{27}{64}$ |
20.若sinα>0,则( )
A. | cos2α>0 | B. | tan2α>0 | C. | $cos\frac{α}{2}>0$ | D. | $tan\frac{α}{2}>0$ |
19.函数f(x)=x2+lnx的零点个数为( )
A. | 0 | B. | 1 | C. | 2 | D. | 3 |
18.已知点A(1,2),B(4,3),向量$\overrightarrow{AC}=({-2,-2})$,则向量$\overrightarrow{BC}$=( )
A. | (-5,-3) | B. | (5,3) | C. | (1,-1) | D. | (-1,-1) |
17.已知集合A={1,2,3,4},B={x|x=2n,n∈A},则A∩B=( )
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A. | {1,4} | B. | {1,3} | C. | {2,4} | D. | {2,3} |