` 1) `
` x . y = -2 `
` => (x;y) ∈ Ư(-2) = {±1 ; ±2} `
Ta có: ` -2 = 1.(-2) = -2.1 = -1.2 = 2.(-1) `
` => (x ; y) = {(1 ; -2) , (-2 ; 1) , (-1 ; 2) , (2 ; -1)} `
Vậy ` (x ; y) = {(1 ; -2) , (-2 ; 1) , (-1 ; 2) , (2 ; -1)} `
` 2) `
` (x - 1)(y - 2) = -3 `
` => {(x - 1);(y - 2)} ∈ Ư(-3) = {±1 ; ±3} `
Ta có: ` -3 = 1.(-3) = -3.1 = -1.3 = 3.(-1) `
` TH1: -3 = 1 . (-3) `
` => x - 1 = 1 <=> x = 2 `
` y - 2 = -3 <=> y = -1 `
` TH2: -3 = -3.1 `
` => x - 1 = -3 <=> x = -2 `
` y - 2 = 1 <=> y = 3 `
` TH3: -3 = -1.3 `
` => x - 1 = -1 <=> x = 0 `
` y - 2 = 3 <=> y = 5 `
` TH4: -3 = 3.(-1) `
` => x - 1 = 3 <=> x = 4 `
` y - 2 = -1 <=> y = 1 `
Vậy ` (x ; y) = {(2 ; -1), (-2 ; 3), (0 ; 5), (4 ; 1)} `
