Is {(1, -3), (-1, 3)} a function or not? I know that a function is when the first coordinate is different, and 1 and -1 are different since one is positive and the other is not, but they’re still 1… please help! Thank you!

You are correct. It is a function.

The Vertical Line Test allows us to know whether or not a graph is actually a function. If a vertical line intersects the graph in all places at exactly one point, then the relation is a function.

You’ll have to plot the points on the graph to do the Vertical Line Test.

To use the vertical-line test, imagine dragging a ruler held vertically across the graph from left to right. If the graph is that of a function, the edge of the ruler would hit the graph only once for every x -value.

Plotting the given points on the graph and performing the Vertical Line Test (VLT) shows that there’s 1 point in each of the vertical lines drawn. This means that the given relation passed the VLT, and that the given set of points represent a function.

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