4.已知函数f(x)=$\left\{\begin{array}{l}{{x}^{2},x<0}\\{{x}^{2}-2ax+2a,x≥0}\end{array}\right.$的图象上恰好有两对关于原点对称的点,则实数a的取值范围是( )
| A. | (4,+∞) | B. | (-∞,0)∪(4,+∞) | C. | (0,4) | D. | (-∞,0) |
3.
设全集U=R,A={x|y=lg(2x-x2)},B={y|y=cos x},则图中阴影部分表示的区间是( )
| A. | [-1,2) | B. | (-1,2) | C. | (-∞,-1)∪[2,+∞) | D. | (-∞,-1]∪[2,+∞) |
19.若函数f(x)=$\left\{\begin{array}{l}{{a}^{x},x>1}\\{-x+3a,x≤1}\end{array}\right.$在R上是单调函数,则实数a的取值范围为( )
| A. | (0,1) | B. | (0,$\frac{1}{2}$] | C. | [$\frac{1}{2}$,1) | D. | (1,+∞) |
18.函数f(x)=ln(x+1)-$\frac{1}{x}$的零点所在的大致区间是( )
0 234046 234054 234060 234064 234070 234072 234076 234082 234084 234090 234096 234100 234102 234106 234112 234114 234120 234124 234126 234130 234132 234136 234138 234140 234141 234142 234144 234145 234146 234148 234150 234154 234156 234160 234162 234166 234172 234174 234180 234184 234186 234190 234196 234202 234204 234210 234214 234216 234222 234226 234232 234240 266669
| A. | (0,1) | B. | (1,2) | C. | (2,e) | D. | (3,4) |