How do you use the vertical line test?

1 Answer
AJ Speller
Sep 30, 2014

The vertical line test is used to find out if a relation is a function.

If a vertical line is drawn for each value in the domain of a relation and if that line only intersects the relation once then the relation is a function.

#y=3x+4# is a line and passes the vertical line test, it is a function.

#y=x^2# is a parabola and passes the vertical line test, it is a function.

#x^2+y^2=1# is a circle and fails the vertical line test, it is not a function.

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