Onto, but not one-to-one

  • Thread starter Jrb599
  • Start date
  • #1
24
0
[SOLVED] Onto, but not one-to-one

I need a function

f: N -> N such that f is onto, but not one-to-one, and I can't think of one to save my life, any suggestions?
 

Answers and Replies

  • #2
EnumaElish
Science Advisor
Homework Helper
2,322
124
f({a,b}) = {x}.

Sorry, you posted N to N...
 
  • #3
24
0
what does {x} stand for?
 
  • #4
EnumaElish
Science Advisor
Homework Helper
2,322
124
f(1) = 2
f(x) = x for x > 1.

Doesn't work.

Hmm...
 
Last edited:
  • #5
24
0
what about

f(1)=1
f(2)=1
f(n) = n-1 for n>2
 
  • #6
EnumaElish
Science Advisor
Homework Helper
2,322
124
I think you have just found one.
 
  • #7
24
0
k, well your original post helped me, so thank you!
 
  • #8
mathwonk
Science Advisor
Homework Helper
2020 Award
11,238
1,444
what about f(x) = 2x? no.....

or greatest integer not greatER THan x/2, +1?

or f(x) = x-1, for x >1 and lets see f(!) = ?

how long did you think about this?
 

Related Threads on Onto, but not one-to-one

  • Last Post
Replies
1
Views
2K
  • Last Post
Replies
1
Views
1K
  • Last Post
Replies
1
Views
2K
  • Last Post
Replies
2
Views
589
Replies
1
Views
4K
Replies
6
Views
1K
  • Last Post
Replies
1
Views
2K
Replies
1
Views
2K
Top