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

Toán Lớp 7: tìm x thuộc Q biết 37-x/ x+13=3/7

Toán Lớp 7: tìm x thuộc Q biết 37-x/ x+13=3/7

Comments ( 2 )

  1. Ta có : ( 37 – x )/( x + 13 ) = 3/7
    ⇔ 7 . ( 37 – x ) = 3 . ( x + 13 )
    ⇔ 259 – 7x = 3x + 39
    ⇔ 259 – 7x – 3x – 39 = 0
    ⇔ 220 – 10x = 0
    ⇔ 10x = 220
    ⇔ x = 220 : 10
    ⇔ x = 22
    Vậy , x = 22 .

  2. {37-x}/{x+13} = 3/7
    $\Rightarrow$ 7 . (37 – x) = 3 . (x + 13)
    $\Rightarrow$ 259 – 7x = 3x + 39
    $\Rightarrow$ -7x – 3x = 39 – 259
    $\Rightarrow$ -10x = -220
    $\Rightarrow$ x = (-220) : (-10)
    $\Rightarrow$ x = 22
    $\text{Vậy}$ x = 22
     

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