Answer:
Function: 2, 4, 5 and 6
Not a function: 1 and 3
Step-by-step explanation:
Vertical line test: If a graph intersect each vertical line at most once, then the graph represents a function.
If the graph passes the vertical line test, then it must be a function.
From the given graph only 1 and 3 fail the vertical line test because they intersect the vertical lines twice. It means 1 and 3 and not a function.
Graph 2, 5 and 6 pass the vertical line test. So, graph 2, 4, 5 and 6 are functions.
In graph 4, there is an open circle at x=2, it means the above piece of graph 4 is not defined for x=2. So, it also passes the vertical line test.
