Answer:
{(1,2),(2,3),(3,4),(4,5)}
Explanation:
A function is any relationship which takes one element of one set and assigns to it one and only one element of the second set.
From the above definition, the relation {(0,2),(0,4),(0,6),(0,8)} is not a function. 0 gives different values, if x=0, it gives 2 or 4 or 6 or 8. It is one-to-many relation
The relation {(1,2),(2,1),(1,3),(3,1)} is not a function, 1 is assigned to 2 or 3.
If x=1,it gives 2 or 3
The relation {(1,2),(3,4),(5,6),(1,8)} is not a function. It is a one - to - many relation. If x=1, it gives 2 or 8
The relation {(1,2),(2,3),(3,4),(4,5)} is a one - to- one relation and it is a function. One and only one value is assigned to only one value of the second set. It is like the function f(x)= x+1
If x=1, f(x)=2
If x=2, f(x)=3
If x=3, f(x)=4
If x=4, f(x)=5