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

Toán Lớp 6: B1 : Tìm x thuộc N , biết a. 1/3 < x/2 < 3/4 b. 1< 10/x < 2 c. 1/2 < 3/x < 4/ 5

Toán Lớp 6: B1 : Tìm x thuộc N , biết
a.
1/3 < x/2 < 3/4 b. 1< 10/x < 2 c. 1/2 < 3/x < 4/ 5

Comments ( 1 )

  1. – Xin ctlhn
    a, $\frac{1}{3}$ < $\frac{x}{2}$ < $\frac{3}{4}$ 
    ⇒ $\frac{4}{12}$ < $\frac{6x}{12}$ < $\frac{9}{12}$ 
    ⇒ 4 < 6x < 9
    – Vì x ∈ N
    ⇒ x = 1
      Vậy x = 1
    b, 1 < $\frac{10}{x}$ < 2
    ⇒ $\frac{10}{10}$ < $\frac{10}{x}$ < $\frac{10}{5}$ 
    ⇒  5 < x < 10
    ⇒ x ∈ { 6 ; 7 ; 8 ; 9 }
     Vậy x ∈ { 6 ; 7 ; 8 ; 9 }
    c, $\frac{1}{2}$ < $\frac{3}{x}$ < $\frac{4}{5}$ 
    ⇒ $\frac{12}{24}$ < $\frac{12}{4x}$ < $\frac{12}{15}$ 
    ⇒ 15 < 4x < 24
    mà x ∈ N
    ⇒ x ∈ { 4 ; 5 }
     Vậy x ∈ { 4 ; 5 }

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

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