Posted by **Lizzy** on Friday, October 5, 2007 at 6:28pm.

relation or function?

x^2 = 1 + y^2

This is a function because relations cannot be an equation right?

- Algebra answer for checking -
**Reiny**, Friday, October 5, 2007 at 7:28pm
Your equation is NOT a function.

If you rearrange it to read : x^2 - y^2 = 1

you should recognize that it is a hyperbola.

Where did you get the idea a relation cannot be an equation?

All relations are equations.

All functions are relations, but only some relations are functions.

The simplest way to determine if a relation is a function is by means of the "vertical line test"

Visualize a vertical line scanning your graph from left to right. If the line cuts your graph in 2 or more points for a given x value, then it is NOT a function.

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