Question

Which relation is a function?

Answer 1

B. To see if it’s a function, it has to pass the vertical line test. That means draw a vertical line (going up and down) through any point on the graph and it can only go through one point. If it goes through more than 1, it’s not a function. Like in graph A, if you draw a vertical line at x=-2, it will go through two points, same at x=2. For graph b, no matter where you move a vertical line, it only passes through one point at a time, so it passes the vertical line test.