问题
选择题
设A={x|x2-2x-3>0},B={x|x2+ax+b≤0},若 A∪B=R,A∩B=(3,4],则a +b等于 ( )
A.7
B.-1
C.1
D.-7
答案
答案:D
A=(-∞,-1)∪(3,+∞),∵A∪B=R,A∩B=(3,4],则B=[-1,4].∵-1,4为方程x2+ax+b=0的两根,∴a=-(-1+4)=-3,b=-1×4=-4,∴a+b=-7.
设A={x|x2-2x-3>0},B={x|x2+ax+b≤0},若 A∪B=R,A∩B=(3,4],则a +b等于 ( )
A.7
B.-1
C.1
D.-7
答案:D
A=(-∞,-1)∪(3,+∞),∵A∪B=R,A∩B=(3,4],则B=[-1,4].∵-1,4为方程x2+ax+b=0的两根,∴a=-(-1+4)=-3,b=-1×4=-4,∴a+b=-7.
Part of A Bus Schedule
A.11:15P B. 6:15P C. 8:15P D. 10:00P 62. Which of the following airport departures does NOT stop at South Station in Boston? A. 9:15 morning bus B. 12:25 afternoon bus C. 5:25 afternoon bus D. 9:25 evening bus 63. According to the schedule, when the service is available, how many buses per day go from Logan Airport to the University of Maine at Orono? A. 1 B. 3 C. 12 D. 17 64. According to the notes under the schedule, when would students NOT be able to get a bus to the University of Maine from Boston? A.At weekends B. In session. C. During university holidays. D. In the case of bad weather 65. Which of the following best describes the ticket policy of Concord Trail ways? A. Tickets must be booked online. B. Reservations are necessary. C. Tickets can be bought on the travel day. D. Discounts are provided for advanced booking. |