13.与直线2x+y-1=0平行,且与圆(x-2)2+(y+1)2=5相切的直线方程是( )
| A. | 2x+y+2=0或2x+y-8=0 | B. | x-2y+1=0或x-2y-9=0 | ||
| C. | 2x+y+1=0或2x+y-9=0 | D. | x-2y+2=0或x-2y-8=0 |
12.已知直线ax+2y-2=0与2x-y+c=0垂直且相交于点(1,m),则a+c=( )
| A. | 1 | B. | -1 | C. | -$\frac{1}{2}$ | D. | $\frac{1}{2}$ |
11.已知直线2x-y+1=0与点(1,-2)为圆心的圆相交于A,B两点,且|AB|=4,则此圆的标准方程是( )
| A. | (x-1)2+(y+2)2=16 | B. | (x-1)2+(y+2)2=9 | C. | (x+1)2+(y-2)2=9 | D. | (x+1)2+(y+2)2=16 |
5.已知$\overrightarrow{a}$=(1,2),$\overrightarrow{b}$=(2,1-x),若$\overrightarrow{a}$与$\overrightarrow{b}$共线,则x等于( )
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| A. | 4 | B. | -3 | C. | 2 | D. | -3或5 |