3.将一次函数y=-3x-2的图象向上平移4个单位长度后,图象不经过( )
| A. | 第一象限 | B. | 第二象限 | C. | 第三象限 | D. | 第四象限 |
1.若不等式组$\left\{\begin{array}{l}{x+a>0}\\{1-2x>x-2}\end{array}\right.$无解,则a的取值范围是( )
| A. | a≤-1 | B. | a<-1 | C. | a≥1 | D. | a>1 |
20.
如图,将△ABC绕着点C顺时针旋转50°后得到△A′B′C′,若∠A=40°,∠B′=110°,则∠A′CB的度数是( )
| A. | 110° | B. | 80° | C. | 40° | D. | 30° |
19.若把分式$\frac{2xy}{x+y}$(x,y为正数)中的x,y分别扩大为原来的2倍,则分式的值是( )
| A. | 扩大为原来的2倍 | B. | 缩小为原来的2倍 | C. | 扩大为原来的4倍 | D. | 不变 |
18.要使$\frac{1}{\sqrt{x-2}}$有意义,x必须满足( )
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| A. | x≤2 | B. | x>2 | C. | x≥2 | D. | x<2 |