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`M = (2x^2 + 10)/(x^2 + 2)`
Để `M` nguyên
`-> 2x^2 + 10 \vdots x^2+2`
`-> 2x^2 + 4 + 6 \vdots x^2+2`
`-> 2 (x^2 +2) + 6 \vdots x^2+2`
Vì `x^2 + 2 \vdots x^2 + 2 -> 2 (x^2+2) \vdots x^2+2`
`->6 \vdots x^2+2`
`->x^2 + 2 ∈ Ư (6) ={1;-1;2;-2;3;-3;6;-6}`
`-> x^2 ∈ {-1; -3; 0; -4; 1; -5; 4; -8}`
Vì `x^2 ≥ 0∀x`
`-> x^2 ∈ {0;1;4}`
`->x^2 ∈ {0; 1^2; (-1)^2; 2^2;(-2)^2}`
`-> x ∈ {0;1;-1;2;-2}`
Vậy `x ∈ {0;1;-1;2;-2}` để `M` nguyên
