令y=(1-x)/(1+x)则x=(1-y)/烂凯(1+y)代入即可f(y)={1-[(1-y)/(1+y)]^2}/{1+-[(1-y)/(1+y)]^2}化简即饥拿唤可。敏举
第五题答案.C;第六题答案.A
c