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222-9+11+12:2*14+14 = ? ( )

Toán Lớp 10: Cho A = (−∞; m), B = [5m − 2; 5m + 5]. Tìm m để a) A ∩ B = ∅. b) B ⊂ A. c) A ⊂ (R \ B). d) (R \ A) ∩ B 6= ∅

Toán Lớp 10: Cho A = (−∞; m), B = [5m − 2; 5m + 5]. Tìm m để
a) A ∩ B = ∅.
b) B ⊂ A.
c) A ⊂ (R \ B).
d) (R \ A) ∩ B 6= ∅

Comments ( 1 )

  1. A=(-oo;m) \qquad B=[5m-2;5m+5]
    a) A∩B=∅
    <=> 5m-2>=m
    <=> 4m>=2
    <=> m>=1/2
    Vậy m>=1/2 thì A∩B=∅
    b) B⊂A
    <=> 5m+5<m
    <=> 4m<-5
    <=> m<-5/4
    Vậy m<-5/4 thì B⊂A
    c) RR\\B=(-oo;5m-2)∪(5m+5;+oo)
    -> A⊂(RR\\B) khi 5m-2>=m
    <=> m>=1/2
    Vậy m>=1/2 thì A⊂(RR\\B)
    d) RR\\A=[m;+oo)
    -> (RR\\A)∩B=∅ khi 5m+5<m
    <=> 4m<-5
    <=> m<-5/4
    Vậy m<-5/4 thì (RR\\A)∩B=∅

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222-9+11+12:2*14+14 = ? ( )

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