第一节 集合的概念与运算
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限时规范训练(限时练·夯基练·提能练)
A级基础夯实练
1.(2019·全国卷Ⅱ)设集合A={x|x2-5x+6>0},B={x|x-1<0},则A∩B=() A.(-∞,1)B.(-2,1)
C.(-3,-1) D.(3,+∞)
解析:选A.A∩B={x|x2-5x+6>0}∩{x|x-1<0}={x|x<2或x>3}∩{x|x<1}={x|x<1}.故选A.
2.(2019·浙江卷)已知全集U={-1,0,1,2,3},集合A={0,1,2},B={-1,0,1},则(∁U A)∩B=()
A.{-1} B.{0,1}
C.{-1,2,3} D.{-1,0,1,3}
解析:选A.∵U={-1,0,1,2,3},A={0,1,2},
∴∁U A={-1,3}.
又∵B={-1,0,1},∴(∁U A)∩B={-1}.
故选A.
3.设集合M={x|x<4},集合N={x|x2-2x<0},则下列关系中正确的是()
A.M∩N=M B.M∪(∁R N)=M
C.N∪(∁R M)=R D.M∪N=M
解析:选D.由题意可得,N=(0,2),M=(-∞,4),N⊆M所以M∪N=M.故选D.
4.已知集合A={0},B={-1,0,1},若A⊆C⊆B,则符合条件的集合C的个数为() A.1 B.2
C.4 D.8
解析:选C.由题意得,含有元素0且是集合B的子集的集合有{0},{0,-1},{0,1},{0,-1,1},即符合条件的集合C共有4个.故选C.
5.设全集U=R,集合A={x∈N|x2<6x},B={x∈N|3 A .{1,2,3,4,5} B .{1,2,3,6,7} C .{5,4} D .{4,5,6,7} 解析:选B.因为A ={x ∈N|x 2<6x }={x ∈N|0 6.集合A =⎩ ⎨⎧⎭ ⎬⎫x ⎪⎪2x >1,B ={x |x 2+x -2>0},则A ∩(∁R B )=( ) A .(0,2) B .(0,1] C .(0,1) D .[0,2] 解析:选B.解法一:解不等式2 x >1,得0 得x <-2或x >1,即B ={x |x <-2或x >1},所以∁R B ={x |-2≤x ≤1},所以A ∩(∁R B )={x |0<x ≤1},故选B. 解法二:取x =1,知1∈A ,1∈∁R B ,则1∈A ∩(∁R B ),排除C ;取x =32,则32∈A , 3 2∉(∁R B ),则3 2 ∉A ∩(∁R B ),排除A ,D ,选B. 7.(2019·广州模拟)已知集合A ={4,a },B ={x ∈Z|x 2-5x +4≥0},若A ∩(∁Z B )≠∅,则实数a 的值为( ) A .2 B .3 C .2或4 D .2或3 解析:选D.因为B ={x ∈Z|x 2-5x +4≥0},所以∁Z B ={x ∈Z|x 2-5x +4<0}={2,3},又集合A ={4,a },若A ∩(∁Z B )≠∅,则a =2或a =3,故选D. 8.(2019·河北六校联考)已知全集U =R ,集合M ={x |x +2a ≥0},N ={x |log 2(x -1)<1},若集合M ∩(∁U N )={x |x =1或x ≥3},那么a 的取值为( ) A .a =12 B .a ≤1 2 C .a =-1 2 D .a ≥1 2 解析:选C.∵log 2(x -1)<1,∴⎩ ⎪⎨⎪⎧x -1>0, x -1<2,即1<x <3,则N ={x |1<x <3},∵U =R , ∴∁U N ={x |x ≤1或x ≥3},又∵M ={x |x +2a ≥0}={x |x ≥-2a },M ∩(∁U N )={x |x =1或x ≥3}, ∴-2a =1,解得a =-1 2 .故选C. 9.已知集合A ={1,2},B ={a ,a 2+3}.若A ∩B ={1},则实数a 的值为________. 解析:∵B ={a ,a 2+3},A ∩B ={1}, ∴a =1或a 2+3=1,∵a ∈R ,∴a =1. 经检验,满足题意. 答案:1 10.(2019·汕头模拟)已知集合A ={1,2,3,4},集合B ={x |x ≤a ,a ∈R},A ∪B =(-∞,5],则a 的值是________. 解析:因为集合A ={1,2,3,4},集合B ={x |x ≤a ,a ∈R},A ∪B =(-∞,5],所以a =5. 答案:5 B 级 能力提升练 11.集合M ={x |2x 2-x -1<0},N ={x |2x +a >0},U =R.若M ∩(∁U N )=∅,则a 的取值范围是( ) A .(1,+∞) B .[1,+∞) C .(-∞,1) D .(-∞,1] 解析:选B.由集合M ={x |2x 2-x -1<0},N ={x |2x +a >0},可得M =⎝⎛⎭⎫-1 2,1,∁U N =⎝⎛⎦⎤-∞,-a 2.要使M ∩(∁U N )=∅,则-a 2≤-1 2 ,解得a ≥1,故选B. 12.(2019·西安三模)已知全集U ={x ∈N|-1≤x ≤9},集合A ={0,1,3,4},集合B ={y |y =2x ,x ∈A },则(∁U A )∩(∁U B )=( ) A .{5,7} B .{-1,5,7,9} C .{5,7,9} D .{-1,1,2,3,4,5,6,7,8,9} 解析:选C.解法一:因为U ={x ∈N|-1≤x ≤9},所以U ={0,1,2,3,4,5,6,7,8,9}.因为集合A ={0,1,3,4},集合B ={y |y =2x ,x ∈A },所以B ={0,2,6,8}.所以∁U A ={2,5,6,7,8,9},∁U B ={1,3,4,5,7,9},所以(∁U A )∩(∁U B )={5,7,9},故选C. 解法二:因为U ={x ∈N|-1≤x ≤9},所以U ={0,1,2,3,4,5,6,7,8,9}.因为集合A ={0,1,3,4},集合B ={y |y =2x ,x ∈A },所以B ={0,2,6,8}.所以A ∪B ={0,1,2,3,4,6,8},所以(∁U A )∩(∁U B )=∁U (A ∪B )={5,7,9},故选C. 13.(2019·杭州模拟)已知集合A ={0,1,2m },B ={x |1<22- x <4},若A ∩B ={1,2m },则实数m 的取值范围是( )