9.已知函数f(x)=x+$\frac{4}{x}$,g(x)=2x+a,若?x1∈[$\frac{1}{2}$,3],?x2∈[2,3],使得f(x1)≥g(x2),则实数a的取值范围是( )
| A. | a≤1 | B. | a≥1 | C. | a≤0 | D. | a≥0 |
8.若函数y=f(x)+cosx在[-$\frac{π}{4},\frac{3π}{4}$]上单调递减,则f(x)可以是( )
| A. | 1 | B. | -sinx | C. | cosx | D. | sinx |
6.已知集合A={(x,y)|y=x2},B={(x,y)|2x-y-1=0},则A∩B=( )
| A. | x=1,y=1 | B. | (1,1) | C. | {1,1} | D. | {(1,1)} |
4.设集合A={0,1},集合B={x|x>a},若A∩B只有一个元素,则实数a的取值范围是( )
| A. | {a|a<1} | B. | {a|a≥1} | C. | {a|0≤a<1} | D. | {a|a≤1} |
3.过点P(-2,0)的直线与抛物线C:y2=4x相交于A,B两点,且|PA|=$\frac{1}{2}$|AB|,则点A到抛物线C的焦点的距离为( )
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| A. | $\frac{5}{3}$ | B. | $\frac{7}{5}$ | C. | $\frac{9}{7}$ | D. | 2 |