Đáp án + Giải thích các bước giải:
`a)`
`2/(n-1) in ZZ <=> 2 vdots n-1`
`=> n-1 in Ư(2)={-2;-1;1;2}`
`=> n in {-1;0;2;3}`
`b)`
`(-2)/(-n+2) in ZZ <=> -2 vdots -n+2`
`=> -n+2 in Ư(-2)={-2;-1;1;2}`
`=> -n in {-4;-3;-1;0}`
`=> n in {4;3;1;0}`
`c)`
`(-3)/(2n-1) in ZZ <=> -3 vdots 2n-1`
`=> 2n-1 in Ư(-3)={-3;-1;1;3}`
`=> 2n in {-2;0;2;4}`
`=> n in {-1;0;1;2}`