8.已知f(x)是R上的奇函数,当x≥0时,f(x)=$\left\{\begin{array}{l}{lo{g}_{\frac{1}{2}}(x+1),0≤x<1}\\{1-|x-3|,x≥1}\end{array}\right.$则函数y=f(x)+$\frac{1}{2}$的所有零点之和是( )
| A. | 1-$\sqrt{2}$ | B. | $\sqrt{2}$-1 | C. | 5-$\sqrt{2}$ | D. | $\sqrt{2}$-5 |
6.已知函数f(x)=lg(ax-bx),(a,b为常数,a>1>b>0),若x∈(2,+∞)时,f(x)>0恒成立,则( )
| A. | a2-b2>1 | B. | a2-b2≥1 | C. | a2-b2<1 | D. | a2-b2≤1 |
1.已知抛物线L的顶点在原点,对称轴为x轴,圆M:x2+y2-2x-4y=0的圆心M和A(x1,y1)、B(x2,y2)两点均在L上,若MA与MB的斜率存在且倾斜角互补,则直线AB的斜率是( )
| A. | -1 | B. | 1 | C. | -4 | D. | 4 |
20.圆心在直线2x-y-6=0上的圆C与y轴交于两点A(0,-5),B(0,-3),则圆C的方程是( )
0 235443 235451 235457 235461 235467 235469 235473 235479 235481 235487 235493 235497 235499 235503 235509 235511 235517 235521 235523 235527 235529 235533 235535 235537 235538 235539 235541 235542 235543 235545 235547 235551 235553 235557 235559 235563 235569 235571 235577 235581 235583 235587 235593 235599 235601 235607 235611 235613 235619 235623 235629 235637 266669
| A. | (x-1)2+(y+4)2=2 | B. | (x+1)2+(y-4)2=2 | C. | (x-1)2+(y-4)2=2 | D. | (x+1)2+(y+4)2=2 |