# Onto fnction

1. Jun 20, 2008

### lipun4u

Determine whether f:Z x Z -> Z is onto if
1> f(m,n) = 2m-n
2> f(m,n) = |m| -|n|

2. Jun 20, 2008

### cristo

Staff Emeritus
You need to show some work before we can help you with your homework. What do you know about onto functions? What have you thought so far?

3. Jun 20, 2008

### lipun4u

ya i kno onto function

i also know how to implement in situation like

f(x)=3x+10

but i don't know ab the above....I guess this is guanine

4. Jun 21, 2008

### HallsofIvy

What is the definition of "onto" function? Do these functions satisfy the definition?
These can be done in exactly the same way as f(x)= 3x+ 10.

Well, not exactly the same- actually these are easier because you have more values to work with.

"guanine"? Isn't that one of the amino acids that make up DNA?

5. Jun 21, 2008

### lipun4u

Can u please explain me how to solve it ????

6. Jun 22, 2008

### HallsofIvy

You said "i also know how to implement in situation like f(x)=3x+10"

Okay, how would you determine whether that is an "onto" function?

What happens if you do exactly the same thing with f(m,n)= 2m- n?

Please show us what you would do with f(x)= 3x+ 10.

7. Jun 22, 2008

### lipun4u

f(x)=y
=> 3x+10 = y
=>x=(y-10)/3

for every value of y there exists a value of x
so its an onto function