x为整数且2x+2/x^2+1也为整数,则2/x^2也为整数,x^2能整除2,故
x=1,或x=-1.
x为整数且2x+2/(x^2+1)也为整数,则2/(x^2+1)也为整数,x^2+1能整除2,故x=1,或x=-1.