` a) ` ` n + 6 \vdots n + 2 `
` => n + 2 + 4 \vdots n + 2 `
Vì ` n + 2 \vdots n + 2 `
` => 4 \vdots n + 2 `
` => n + 2 ∈ Ư(4) = {±1 ; ±2 ; ±4} `
` => n ∈ {-3 ; -1 ; -4 ; 0 ; -6 ; 2} `
` b) ` ` 2n + 3 \vdots n - 2 `
` => 2n - 4 + 7 \vdots n - 2 `
Vì ` 2n - 4 \vdots n - 2 `
` => 7 \vdots n - 2 `
` => n - 2 ∈ Ư(7) = {±1 ; ±7} `
` => n ∈ {1 ; 3 ; -5 ; 9} `
` c) ` ` 3n + 1 \vdots 11 - 2n `
` => -3n - 1 \vdots 11 - 2n `
` => -1 - 3n \vdots 11 - 2n `
` => 2.(-1 - 3n) \vdots 11 - 2n `
` => -2n - 6n \vdots 11 - 2n `
` => 33 - 6n - 35 \vdots 11 - 2n `
Vì ` 33 - 6n \vdots 11 - 2n `
` => -35 \vdots 11- 2n `
` => 11 - 2n ∈ Ư(-35) = {±1 ; ±5 ; ±7 ; ±35} `
` => 2n ∈ {12 ; 10 ; 16 ; 6 ; 18 ; 4 ; 46 ; -24} `
` => n ∈ {6 ; 5 ; 8 ; 3 ; 9 ; 2 ; 23 ; -12} `
