x/(x-1)+k/(x+1)-x/(x+1)=0
x(x+1)+k(x-1)-x(x-1)=0
x(x+1)+k(x-1)-x(x-1)=0
x^2+x+kx-k-x^2+x=0
2x+kx-k=0
(2+k)x-k=0
(2+k)x=k
x=k/(2+k)
根据无解就是方程不等于0得:
k不等于-2.