回复：your (2) means f is bijection function. 1 to 1 and onto.

1) and 2) can be obtained by f(f(n))=n+c

所有跟帖： 

• If f is linear, OK. But we can't say nonlinear f is impossible b -jinjing- ♀ (45 bytes) () 06/01/2011 postreply 11:41:54

• you said yourself "for any f, no solution" -15少- ♂ (41 bytes) () 06/01/2011 postreply 13:14:55

• 回复：you said yourself "for any f, no solution" -jinjing- ♀ (55 bytes) () 06/01/2011 postreply 14:28:17

• is there anything wrong in my demonstration 1) to 6)? -15少- ♂ (0 bytes) () 06/01/2011 postreply 15:06:40

• your answer is not math answer, I do this Q, I hope you can see. -jinjing- ♀ (191 bytes) () 06/02/2011 postreply 10:07:19

• MY answer is MY math answer. -15少- ♂ (299 bytes) () 06/02/2011 postreply 12:41:02

• I like the people who like Math. Let me tell you the detail. -jinjing- ♀ (177 bytes) () 06/02/2011 postreply 15:51:05

• 回复：I like math, not myth nor mystification -15少- ♂ (266 bytes) () 06/02/2011 postreply 17:24:06

• You at first you don't think f(N1)=N2,so,I ,,,,your deduce prove -jinjing- ♀ (164 bytes) () 06/02/2011 postreply 18:23:04