Final answer:
The relation is not a function because the x-value '6' is associated with two different y-values, violating the definition of a function that requires each input to have a single output.
Step-by-step explanation:
Whether the given relation {(6,5),(4,3), (6,4), (5,8)} is a function can be determined by checking if any x-value is associated with more than one y-value. A function must have exactly one output for each input. In this relation, the x-value '6' corresponds to two different y-values ('5' and '4'). Therefore, it fails the definition of a function as it shows a dependence of y on x isn't unique for each x.
Answer:
b) No