a) x−12 nguyên⇔(x-1)∈Ư(2)={±1;±2}
Nếu x-1=-1 ⇔ x= 0
Nếu x-1=1 ⇔ x= 2
Nếu x-1=-2 ⇔ x=-1
Nếu x-1=2 ⇔ x= 3
⇒x∈{-1;0;2;3}
b) 3x−2−6 nguyên ⇔(3x-2)∈{±1;±2;±3;±6}
c) x−1x−2 = 1−x−11 nguyên⇔ (x-1)∈{±1}
Khi x-1=-1⇔x=0
Khi x-1=1⇔x=2
Vậy x∈{0;2}
d)x−52x+3 =2+x−513 nguyên ⇔(x-5)∈Ư(13)={±1;±13}