Explicație pas cu pas:
(x²-x+2)/(x²-1) €Z <=>x²-1|x²-x+2
x²-1|x²-x+2
x²-1|x²-1
=> x²-1|x²-x+2-x²+1 =>x²-1|3-x
x²-1|3-x/*x =>x²-1|3x-x²
x²-1|x²-1
=> x²-1|3x-x²+x²-1 => x²-1|3x-1
x²-1|3x-1
x²-1|3-x/*3=>x²-1|9-3x
=>x²-1|3x-1+9-3x=>x²-1|8=>x²-1€D8 in Z =>
x²-1€{-8,-4,-2,-1,1,2,4,8} =>
x²€{-7,-3,-1,0,2,3,5,9}
Cum x€Z => x²€{0,9}=>
x€{0,3,-3} => S€{0,3} (nu luam -3 deoarece fractia nu mai €Z)