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

Toán Lớp 7: Tìm x và y (12x-5)(4x-1)+(3x-7)(1-16x)=81

Toán Lớp 7: Tìm x và y
(12x-5)(4x-1)+(3x-7)(1-16x)=81

Comments ( 2 )

  1. (12x – 5)(4x – 1) + (3x – 7)(1 – 16x) = 81
    ⇒ 48x^{2} – 12x – 20x + 5 + 3x – 48x^{2} – 7 + 112x = 81
    ⇒ 83x – 2 = 81
    ⇒ 83x = 83
    ⇒ x = 1
     

  2. (12x-5)(4x-1)+(3x-7)(1-16x)=81
    (12x-5)(4x-1)+(3x-7)(1-16x)
    =-32x+115x-2
    =83x-2
    ⇒83x-2=81
       83x=81+2
       83x=83
       x=83:83
       =>x=1

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

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