How do find if a relation is a function algebraically Is there a way to see if a relation is a function without having to do a "vertical line test" (where you draw a vertical line on the graph and if there line touches two points then it's not a function).
To determine if a function is even or odd you simply go f(x) = f(-x); even, f(-x) = -f(x); odd. Can I do something similar to find out if a relation is a function?
Thanks

For a relation to be a function, it must be one-to-one or injective, meaning that it must map each input into a different output.
If you can't use the vertical line test, see if you can determine whether or not the function/relation has branches.
