用1/(1-x)代替x代入原式,得到
2/(1-x) f[1/(1-x)[ + f[(x-1)/x] = 2/(1-x)
再用(x-1)/x代入原式,得到
2(x-1)/x f[(x-1)/x] + f(x) = 2(x-1)/x
利用这三个方程可以解出f(x)