Đáp án+Giải thích các bước giải:
`đk:x in Z`
`A in Z`
`=>5-x vdots x-2`
`=>-(x-2)-2+5 vdots x-2`
`=>-(x-2)+3 vdots x-2`
`=>3 vdots x-2` do `-(x-2) vdots x-2`
`=>x-2 in Ư(3)={1,-1,3,-3}`
`+)x-2=1=>x=3(tm)`
`+)x-2=-1=>x=1(tm)`
`+)x-2=3=>x=5(tm)`
`+)x-2=-3=>x=-1(tm)`
Vậy `x in {1,-1,3,5}` thì `A in Z`