Answer:
A relation is (also) a function if every input x is mapped to a unique output y.
In terms of graphical representation, this implies that a graph represents a function if there doesn't exist a vertical line that intersects the graph more than once. So:
The first graph is exactly a vertical line, so it's not a function.
The second graph represents the function y=x, so it's a function: you can see that every possible vertical line crosses the graph only once.
The third graph is not a function, because you can draw vertical lines that cross the graph twice.
Similarly, in the fourth graph you can draw vertical lines that cross the graph twice
The fifth graph is a function, because every vertical line crosses the graph once
The last graph is a function, although discontinuous, for the same reason.
Read more on Brainly.com - https://brainly.com/question/14474392#readmore
Step-by-step explanation: