# Vertical Line Test

The vertical line test can be used to determine if a curve is the graph of a function. The vertical line test determines if for every value of x there is only one output y corresponding to it.
The picture below shows the graph of the function and the line . By adjusting the values of , check that passes the vertical line test, i.e. for every value of there is only one output corresponding to it.

## Graph of h(x)

What about the curve below, does it pass vertical line test?
Does this curve represent a function? Explain why.

Can you think of what features a curve must have to be the graph of a function? Perhaps contrast these two graphs.

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