令2(x+1)/(x-1)=k,k为整数得x=(k+2)/(k-2)=1+4/(k-2)为整数则4/(k-2)为整数即4/(k-2)=-4,-2,-1,1,2,4即k=1,x=-3 k=0,x=-1 k=-2,x=0 k=6,x=2 k=4,x=3 k=3,x=5故x=-3,-1,0,2,3,5.
除1外的奇数(或者负的)明显可以x=2n分式=(4n+4-2)/(2n-1)=2+4/(2n-1)2n-1要整除4x=2or0