Question

Is the following relation a function ?

Answer 1

No  because it fails the vertical line test.  Note that  a vertical line can be drawn  through the graph which passes through 2 points. If it was a function any vertical line would pass through   only one point on the graph.

Answer 2

No, it is not a function. It fails the vertical line test (VLT). VLT state that if you draw a vertical line, it must only intersect the graph one time. If it intersections more than once, then it is not a function.