={x|ax2+2x+a=0,a∈R.},若集合A.有且仅有2个子集,则实数a的取值是( ) A.1 0,1 -1, 1 -1,0,1
={x|x2-x-2≤0},集合 为整数集,则A.∩B.=( ) A.{-1,0,1,2}B.{-2,-1,0,1} {0,1} {-1,0}
={3,a2},集合 ={0,b,1-a},且A.∩B.={1},则A.∪B.=( ) A.{0,1,3}B.{1,2,4} {0,1,2,3} {0,1,2,3,4}
={0,1},则满足条件A.∪ ={0,1,2,3}的集合B.共有( ) A.1个 B.2个 3个 4个