20.已知圆x2+y2+2x-2y+2a=0截直线x+y+2=0所得弦长为4,则实数a的值是( )
| A. | -1 | B. | -2 | C. | -3 | D. | -4 |
19.下列命题错误的是( )
| A. | “若x≠a且x≠b,则x2-(a+b)x+ab≠0”的否命题是“若x=a或x=b,则x2-(a+b)x+ab=0” | |
| B. | 若p∧q为假命题,则p,q均为假命题 | |
| C. | 命题“?x0∈(0,+∞)lnx0=x0-1”的否定是“?x∈(0,+∞),lnx≠x-1 | |
| D. | “x>2”是“$\frac{1}{x}$<$\frac{1}{2}$”的充分不必要条件 |
18.已知直线ax+y+2=0的倾斜角为$\frac{3}{4}$π,则该直线的纵截距等于( )
0 226498 226506 226512 226516 226522 226524 226528 226534 226536 226542 226548 226552 226554 226558 226564 226566 226572 226576 226578 226582 226584 226588 226590 226592 226593 226594 226596 226597 226598 226600 226602 226606 226608 226612 226614 226618 226624 226626 226632 226636 226638 226642 226648 226654 226656 226662 226666 226668 226674 226678 226684 226692 266669
| A. | 1 | B. | -1 | C. | 2 | D. | -2 |