Question

Explain how the vertical line test can help determine if a graph is a function

Answer 1

because if you do the vertical line test and two points vertically are in the same line, then it is not a function

Answer 2

If you draw a vertical line and there are two points on it it can't be a function because there are two y coordinates for an x coordinate on the line.

Answer 3

its only useful if you now all possible points, and if you can draw a perfectly vertical line ... in other words it tends to be fairly useless.

Answer 4

If you draw a vetical line and it goes through your equation 2 times, then it is a function. If it is less than 2 times, it is not a function.