两边对 x 求导，得f(x) + f(x) + (x-1)f'(x) = 0,(x-1)f'(x) = -2f(x) x ≠ 1 时, df(x)/f(x) = -2/(x-1),ln[f(x)] = -2ln(x-1)+lnCf(x) = C/(x-1)^2x = 0 时，-f(0) = 1， f(0) = -1,得 C= -1， 则 f(x) = -1/(x-1)^2
