20.下列一元二次方程中,没有实数根的是( )
| A. | x2-2x-1=0 | B. | x2-2x+1=0 | C. | x2-1=0 | D. | x2+2x+3=0 |
11.在平面直角坐标系中,点(5,3)关于x轴的对称点是( )
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| A. | (3,5) | B. | (5,-3) | C. | (-5,3) | D. | (-5,-3) |