To solve this using the vertical line test, graph the points then see if any of them fall on the same vertical line (vertical lines run up and down), or in other words, see if any point is right above another. If there are any like this, then the graph is not a function. To graph the points from a t-chart, use one x-value, and the y-value right next to (or above it) as one point. For example, the first x-value is -3 and the first y-value is -4. Put these together as the first point: (-3, -4).