令 t = √x+1 ,
则有：√x = t-1 ,x = (t-1)² ,
已知,f(√x+1) = x/(2-√x) ,
可得：f(t) = (t-1)²/[2-(t-1)] = (t-1)²/(3-t) ,
所以,f(x) 的解析式为 (x-1)²/(3-x) .