20.若0<x<y<1,则下列不等式成立的是( )
A. | ($\frac{1}{2}$)x<($\frac{1}{2}$)y | B. | x${\;}^{-\frac{1}{3}}$<y${\;}^{-\frac{1}{3}}$ | C. | logx$\frac{1}{2}$<logy$\frac{1}{2}$ | D. | logx3<logy3 |
18.已知全集U={1,2,3,4,5,6,7,8},集合A={2,3,5},集合B={1,3,4,6,7},则集合A∩∁UB=( )
A. | {3} | B. | {2,5} | C. | {2,3,5} | D. | {2,3,5,8} |
17.等差数列{an}的前n项和为Sn,若a2+a7+a12=15,则S13的值是( )
A. | 45 | B. | 65 | C. | 80 | D. | 130 |
16.命题“$?x∈(0,\frac{π}{2}),sinx+cosx>1$”的否定是( )
A. | $?x∈(0,\frac{π}{2}),sinx+cosx≤1$ | B. | $?x∉(0,\frac{π}{2}),sinx+cosx>1$ | ||
C. | $?{x_0}∈(0,\frac{π}{2}),sin{x_0}+cos{x_0}≤1$ | D. | $?{x_0}∈(0,\frac{π}{2}),sin{x_0}+cos{x_0}>1$ |
15.集合A={x|(x-1)(x+2)<0},集合B={x|lgx≤0},则A∩B=( )
A. | (0,1) | B. | (0,1] | C. | (-2,1] | D. | (-2,1) |
14.若函数f(x)=3cosωx(ω>0)在(0,π)上恰有一个最大值和一个最小值,则ω的取值范围是( )
A. | ($\frac{1}{4},1$] | B. | (1,$\frac{3}{2}$] | C. | ($\frac{3}{2},\frac{8}{5}$] | D. | (2,3] |
11.能使不等式f(x)≤M成立的所有常数M中,我们把M的最小值叫做f(x)的上确界,若a>0,b>0且a+b=1,则$-\frac{1}{2a}-\frac{2}{b}$的上确界为( )
0 250891 250899 250905 250909 250915 250917 250921 250927 250929 250935 250941 250945 250947 250951 250957 250959 250965 250969 250971 250975 250977 250981 250983 250985 250986 250987 250989 250990 250991 250993 250995 250999 251001 251005 251007 251011 251017 251019 251025 251029 251031 251035 251041 251047 251049 251055 251059 251061 251067 251071 251077 251085 266669
A. | $-\frac{9}{2}$ | B. | $\frac{9}{2}$ | C. | $\frac{1}{4}$ | D. | -4 |