已知A={1,2,a^2-3a-1},B={1,3},A∩B{3,1}则a等于已知A={1,2,a^2-3a-1},B={1,3},A∩B{3,1}则a等于A.-4或1B.-1或4C.-1D.4

来源:学生作业帮助网 编辑:作业帮 时间:2024/11/06 05:09:45
已知A={1,2,a^2-3a-1},B={1,3},A∩B{3,1}则a等于已知A={1,2,a^2-3a-1},B={1,3},A∩B{3,1}则a等于A.-4或1B.-1或4C.-1D.4
x͐J@_ť8M@FC>]@h Y+RB|$IE\W==mҗfd6i#b9Q[CN&>:>ʺAvi=2`S:wI8{ylŏyq'ޏ?tfڍP29gW>M?

已知A={1,2,a^2-3a-1},B={1,3},A∩B{3,1}则a等于已知A={1,2,a^2-3a-1},B={1,3},A∩B{3,1}则a等于A.-4或1B.-1或4C.-1D.4
已知A={1,2,a^2-3a-1},B={1,3},A∩B{3,1}则a等于
已知A={1,2,a^2-3a-1},B={1,3},A∩B{3,1}则a等于
A.-4或1
B.-1或4
C.-1
D.4

已知A={1,2,a^2-3a-1},B={1,3},A∩B{3,1}则a等于已知A={1,2,a^2-3a-1},B={1,3},A∩B{3,1}则a等于A.-4或1B.-1或4C.-1D.4
因为A={1,2,a^2-3a-1},B={1,3},A∩B{3,1}
所以
a^2-3a-1=3
a^2-3a-4=0
(a-4)(a+1)=0
所以a=-1或者a=4
选择b

选B
A∩B={3,1} 说明A,B里都有1和3这个数,那现在你知道A里已有1,那么a^2-3a-1=3
就求出B答案了