20.已知椭圆C:$\frac{{x}^{2}}{6}$+$\frac{{y}^{2}}{9}$=1,若P(x,y)是椭圆C上一动点,则x2+y2-2x的取值范围是( )
| A. | [6-2$\sqrt{6}$,9] | B. | [6-2$\sqrt{6}$,11] | C. | [6+2$\sqrt{6}$,9] | D. | [6+2$\sqrt{6}$,11] |
19.定义运算a⊕b=$\left\{\begin{array}{l}a\begin{array}{l}{\;},{a<b}\end{array}\\ b\begin{array}{l}{\;},{a≥b}\end{array}\end{array}$若函数f(x)=2x⊕2-x,则f(x)的值域是( )
| A. | [1,+∞) | B. | (0,+∞) | C. | (0,1] | D. | $[{\frac{1}{2},1}]$ |
18.集合M={x|x2-x-6≥0},集合N={x|-3≤x≤1},则N∩(∁RM)等于( )
0 235853 235861 235867 235871 235877 235879 235883 235889 235891 235897 235903 235907 235909 235913 235919 235921 235927 235931 235933 235937 235939 235943 235945 235947 235948 235949 235951 235952 235953 235955 235957 235961 235963 235967 235969 235973 235979 235981 235987 235991 235993 235997 236003 236009 236011 236017 236021 236023 236029 236033 236039 236047 266669
| A. | [-2,1] | B. | (-2,1] | C. | [-3,3) | D. | (-2,3) |