Answer:
2 and 4
Step-by-step explanation:
A relation describe a function when for every x is associated one and only one y
1) is not a function because when x = 1 there are two y associated (3 and 5)
2) yes, for the definition of function
3) is not a function because when x = 5 there are four y associated ( 5, 4, 3, 2)
4) yes, because for every x there is only one y associated (is not important if is the same)
