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

Toán Lớp 6: Tìm x biết : x + ( x + 1 ) + ( x + 2 ) + … + 20 = 20

Toán Lớp 6: Tìm x biết :
x + ( x + 1 ) + ( x + 2 ) + … + 20 = 20

Comments ( 2 )

  1. x + ( x + 1 ) + ( x + 2 ) + … + ( x + 20) = 20
    => \underbrace{(x + x + x + … + x)}_{21    số} + \underbrace{(1 + 2 + … + 20)}_{20    số} = 20
    => x . 21 + 210 = 20
    => x . 21 = 20 – 210
    => x . 21 = -190
    => x = (-190) : 21
    => x = -190/21
    Vậy x = -190/21
    #dtkc
     

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

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