10.设a,b是实数,命题“?ab>0,都有a>0,b>0”的否定是( )
A. | ?ab≤0,使得a≤0,b≤0 | B. | ?ab≤0,使得a≤0或b≤0 | ||
C. | ?ab>0,使得a≤0,b≤0 | D. | ?ab>0,使得a≤0或b≤0 |
9.设奇函数f(x)在(0,+∞)上为单调递增函数,且f(2)=0,则不等式$\frac{{f({-x})-f(x)}}{x}≥0$的解集( )
A. | [-2,0]∪[2,+∞) | B. | (-∞,-2]∪(0,2] | C. | (-∞,-2]∪[2,+∞) | D. | [-2,0)∪(0,2] |
8.如图,∠C=$\frac{π}{2}$,AC=BC,M、N分别是BC、AB的中点,将△BMN沿直线MN折起,使二面角B′-MN-B的大小为$\frac{π}{3}$,则B'N与平面ABC所成角的正切值是( )
A. | $\frac{{\sqrt{2}}}{5}$ | B. | $\frac{4}{5}$ | C. | $\frac{{\sqrt{3}}}{5}$ | D. | $\frac{{\sqrt{15}}}{5}$ |
4.已知集合A={(x,y)|y=x2},B={(x,y)|y=x},则A∩B=( )
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A. | {0,1} | B. | {(0,0),(1,1)} | C. | {1} | D. | {(1,1)} |