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

Toán Lớp 8: Tìm n thuộc Z để 3n^2-n+2 ⋮ n+1 (giúp mik với )

Toán Lớp 8: Tìm n thuộc Z để 3n^2-n+2 ⋮ n+1 (giúp mik với )

Comments ( 2 )

  1. 3n² – n + 2 $\vdots$ n + 1
    3n² + 3n – 4n + 2 $\vdots$ n + 1
    3n ( n + 1 ) – 4n + 2 $\vdots$ n + 1
    3n ( n + 1 ) – 4n – 4 + 6 $\vdots$ n + 1
    3n ( n + 1 ) – 4 ( n + 1 ) + 6 $\vdots$ n + 1
    ( 3n – 4 ) ( n + 1 ) + 6 $\vdots$ n + 1
    3n – 4 + 6 $\vdots$ n + 1
    3n + 2 $\vdots$ n + 1
    3n + 3 – 1 $\vdots$ n + 1
    3 ( n + 1 ) – 1 $\vdots$ n + 1
    -1 $\vdots$ n + 1
    ⇒ n + 1 ∈ Ư ( -1 ) = { ±1 }
    TH 1 : n + 1 = 1 ⇒ n = 0
    TH2 : n + 1 = -1 ⇒ n = -2
     Vậy n = { 0 ; -2 } thì 3n² – n + 1 $\vdots$ n + 1

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