设f(x)=(ax+b)/(cx+d)则:(a+bx)/(c+dx)=-(ax+b)/(cx+d)比较系数,得:bc+ad=0bd+ac=0只要满足以上两试的a,b,c,d就可以取一特例:a=1,b=-1,c=1,d=1f(x)=(x-1)/(x+1)