(x + k)/(x + 1) - k/(x - 1) = 1
(x-1)(x + k)/(x + 1)(x - 1) - k(x + 1)/(x + 1)(x - 1) = 1
(x - 1)(x + k) - k(x + 1) = (x + 1)(x - 1)
x^2 + kx - x - k - kx - k = x^2 - 1
-x - 2k = -1
x = 1 - 2k
x = 1 - 2k
这即是原分式方程的解,
因为分式方程的解为负数,
所以, 1 - 2k < 0
解此不等式得: k > 1/2